I've been to the vet.. Kitten sneezing lots of mucus

Hi there,
I have a beautiful kittien, he is about 14 weeks old, we rescued him a few weeks ago from a farm, he came with a snotty nose.
The next day I took him to the vet for his shots and to check on his runny nose, the vet took his temp, said it was normal and dismissed the running nose as a bit of a chill, (he was sleeping outside at the farm) and said it would go away in a few days, well a week later it still was running, and proper mucus, when he sneezes green mucus flies.. So I took him back and he gave him some antibiotics, by the 3rd day of the 5 day course the mucus and sneexing was gone I was so pleased, then about on the 8/9 th day his nose started running again. I took him back for more antibiotics and the vet said maybe he just needs another course.. Well same outcome. He Is still sneezing and full of mucus. I don't want to put him on a third course. I feel so bad for him because when he sleeps it all gathers around his little nose and then he wakes up in a panic cos he can't breath.. I see he has started sleeping with his mouth open but that's also no good.. So I'm battling to sleep at night because I'm sitting over him with wet wipes, constantly wiping his face so that he doesn't have to choke and freak out.. He is so little, he was the runt of the litter so I thought maybe it could be his lungs that didn't fully develop or could be something completely unrelated.. Also it's not contagious because I have another kitten just a few weeks older than him and she hasn't gotten sick and they have been together now for almost 2 months..
He snores like crazy, but is very playful and has a good appetite so I don't think he is sick but there definitely is something wrong.. So any advice would be much appreciated. Thanks so much!

First off let me say that you are a very good mommy, being so diligent in taking care of the little guy! He is very lucky to have found you!

Sylvester had something similar a few weeks ago, his mucus stayed clear so I didn't take him to the vet as I also didn't want to stress him out, he has only been to the vet twice in his life, but I talked to them and they said try L-Lysine which is supposed to help with immune and respiratory issues, although I read some reports that say they don't believe it works in cats like it does humans? I also had given him some Transfer Factors Plus (colostrum) which usually helps but he seemed like it upset his stomach so we knocked that off. He is much better, but still has a cough that is lingering a bit and snorts and sneezes here and there, but is much better. In fact I am going to post a thread asking if that is normal or not, I hope it is nothing going to be "chronic" with him. If he needs to go to the vet he will, but I really don't have a lot of faith in some of them, some want to give Convenia antibiotic shots all the time and that's not always good, but we'll see.

Good luck, I hope others chime in here and the little guy feels better soon!

This seems to be a fairly common problem. Im having issues with my guy similar to this. I have already spent well over $1000 trying to find a solution. Antibiotics work for my cat but as soon as the antibiotics stop it comes back again.
If your kitten has green nasal discharge he really needs antibiotics though. There is an infection in there.
Some things my guy has been through that you could ask your vet about...

Culture test on the nasal discharge and blood tests to check for any nasties. More specifically the FHV virus. The herpesvirus is one of the most common causes for upper respiratory infections like these. 

Skull xrays to check for any foreign bodies that he may have inhaled such as grass seeds or similar.

A thorough dental and mouth exam. My vet missed a bad tooth which is being extracted tomorrow.

A rhinoscopy to look for any issues with in the nasal cavity, however this is fairly limited. They can't see very deep in to the cats nasal passages.

A nasal flush which should be done at the same time he is under for xrays and or rhinoscopy.

An allergy test or trial or an antihistamine to rule out allergy.

I also changed his food a number of times in case of food allergy.

Some more controversial treatments i have also tried with no results have been Lysine @ 500mg twice a day. This is to help with the FHV if it's there. And a good probiotic however this was more to help with the on going use of antibiotics. Antibiotics kill off good bacteria as well as bad so i was trying to help the good stuff return. If you try this you should wait for a few hours after giving the antibiotic. For me there was no apparent results at all.

That's all iv got for you at the moment. Aside from the tooth extraction my cat has had all of this done and still no solution. The only thing that has worked is antibiotics however seen as the problem returns, it is just a band aid. The actual cause of the issue remain illusive. Both vets i have taken him to have said this kind of thing is known for being hard to find a solution for. 

Thank you for your advice, there could be so many things. It's so frustrating because some days the mucus is clear and some days it's more cloudy and greenish.. I'm taking him next week for his booster shot so hopefully the vet can check him out again.. Thank you again.