Rippling of the skin - could it be FHS?

Since October 2014 I adopted a cat from the shelter. She initially came here with me from for a only a short period, because I socialize kittens and she was my foster mommy cat and had her kittens here too.

I decided to keep her. I don't know much about her history. She is estimated around three years, and this was her second litter in a short time.
So she has been through a lot.
 

I lately started to notice that she has often those ripplings down her coat in her lower back. The rippling of the skin sometimes comes out of nowhere, which means I don't see any cause. Sometimes I also see her doing it after seeing a dog in front of her, for example. She is doing it a couple times a day.
She didn't jump easily for two days or so. I  went to the vet and she exerted some pressure on the back and it hurt, because she started growling softly.
On the advice of the vet we did a X-ray of her back to see if any vertebrae had shifted. Her back looked basically good, no displaced vertebrae. Only the piece at the lower back and the sacrum was a bit 'whiter' than usual. It may be that this has been too much forced, also possible due to the fact she had given birth at least two times. 
She now has to take Novacam for two weeks (only two days left now)  and my vet said she had to make progress in those two weeks. So no more rippling, unless there was a real reason, such as a stress situation.
She has no problems with jumping for as far I can see. However, I don't see any change of the rippling of the skin. I wonder whether this is a sign of pain or stress, or both? She obviously has been through quite a lot and the x-ray showed normal, except that part around the sacrum which was whiter than usual.
I have quite much stress myself now, and she is quite sensitive, so see possibly feels this and get stressed too?
What would you advice me? Could it be FHS? She has no other symptoms such as biting, licking, chasing her tail etc. Occasionally she sometimes has a hyper-attack and then she runs behind my other cat, but then they just play. She eats well too.
Anyone any idea if this is FHS or just stress or perhaps something else?
Also a question in general : What works really well against stress in cats? I have looked for Zylkene and some other medication but I do not know what works well and is harmless as well. I also have valerian cushions and I try to provide as much rest as possible with minimal changes.

This week I should contact my vet again to tell her how things are going. She is doing fine though except for the ripplings. I don't want her any longer on novacam or similar medication because of the side effects it can have.

Both of my cats have skin rippling. They are from the same litter so I assumed it was a genetic problem. The rippling does not affect them at all. No freaking out, yelling, biting the tail, no nothing. This has been ongoing since they were kittens, and they are 5.5 years old now. No health problems, just occasional rippling. While this may not be the case with your cat, it is something to consider. As for stress, try Feliway 

I also use Feliway plug ins & also calming treats you can get on Amazon. They work relatively well. I have 1 cat that has a rippling back also. I never knew it was a thing until I saw it on an episode of My Cat from Hell. For my cat, its just when she gets agitated (which is often). But that's it, just some rippling, an evil stare, a growl...then on with life. She'll occasionally reach back & lick with a passion for 3-4 seconds, then its over. So rippling does not automatically mean a serious problem. 

Also if it happens every day?

I am trying to figure out what it could be. She has had blood tests earlier and her blood levels were OK. She is also tested on FIV and FeLV. She had no FIV or Felv.

She has had an ultrasound for her belly since she had a spot on her belly. It has been removed and the spot was tested and it was no tumor or anything else. It was an extreme reaction on the stitches on her belly.

The X-ray didn't show anything abnormal, except the fact that a part of a bone near her sacrum was more white than usual, which seems a little bit vague to me?

So, actually , every day, usually in the evening, she seems hyperactive. This takes a few minutes. Sometimes she'll go running through the house just chasing after nothing, but sometimes she runs after one of my other cats and at the end they play together.

I will talk with my vet about it but I am just trying to figure out what's going on. It's also weird she started growling when the vet tested her lower back. So it must be painful?
However, since she is using pain medication now, she still has these ripplings as much as before. Then I start thinking, these ripplings are no sign of pain?

Sometimes I think i have to change her diet. Because she might be allergic or so? Or is this a small chance? I give her high quality food though but food can influence a lot of things so.. 

I hope she doesn't have pain anyway and I hope she isn't too stressed. I will try calming treats. Feliway is quite expensive and I hear lots of people saying that they don't see any difference?

In my opinion, the best thing for stress is playtime.  And if it IS FHS, so what?  There is nothing much you can do about it except feed her good food (maybe this helps, maybe not), so try not to worry.  But, honestly, it doesn't sound like FHS.  Or if it is, it sounds pretty mild. 

OH, one other thing you can try for stress is essential oils, like Rescue Remedy for Pets.  There are others, this is just the first one that popped into my mind. 

Next time you talk to your Vet, ask for a clear definition of what "more white than usual" means   That's kind of odd, but hopefully doesn't mean anything . 

Because of the pain she had on her back, and the x-rays showing that minor bone issue, I'm thinking this sounds as if she gets some minor inflammation or discomfort maybe in that area. Discomfort could be causing the rippling. That's the whole thing about FHS, the cat feels a sensation that causes them to think something's hurting them/attacking them. It sounds as though your cat's issue isn't as severe, or there would be racing around the room, biting/licking tail, growling, etc. Maybe what she's feeling is more like an itch/twitch/poke. The other thing it could be is itchy skin. My cat had really dry skin a while back (when petting her you could just hear the crackling of static electricity) when the winter was horribly dry and had a month where she was rippling and running away scared as if something was bothering her. Once the skin stopped bothering her, the rippling went away. I was worried that my cat's behavior was FHS too, but thankfully it wasn't. I would talk with your vet about it, and especially if it gets worse and she starts acting scared/violent.

Honestly though, if she doesn't appear agitated or scared beyond just rippling skin, it may just be the way she shows excitement or stress.

Thanks for the advice

I will ask my vet about FHS and if she can give me some more information about the X-ray. A small part of the bone was more white than usual, which possibly means it has been forced, e.g. when she gave birth. That's what I understood. 
I will also find something for her to reduce the possible stress she might have. 

She eats well, drinks well, she is interested in her surrounding. The only thing is, that apart from the ripplings, she has these hyperactive moments, usually once a day. Her pupils get big, she starts to jump off the couch, runs upstairs, runs back downstairs, while nothing really happened. When she sees one of my other cats she chase after them and sometimes they want to play together, and sometimes my other cats don't want to play and they will run away so she will run even faster.

That's why I thought of FHS, because the combination of the ripplings and the hyperactive moments. My other cats have these moments too sometimes, but definitely not every day. It only takes about 5 or 10 minutes or so and rarely more than once a day, but I don't know if this is normal for a cat?

I give her all my love and attention though And try to keep things the same. 

Maybe it is seasonal, I don't know, since I adopted her in October. The weather is getting better soon so perhaps the ripplings will stop.. But anyway, of course I keep checkin on her  

Well, I will ask my vet what to do now. Thanks for the advice again