Kitten not using litter box (Yes, another one of these)

Hello all. Let me start off with a little background. We have 3 cats, a 4 year old male Persian, a 7 month old female Bengal, and a 7 month old male DSH (similar looking to a Russian Blue) Bruce, Harley, and Grayson (Any Batman fans out there?) Anywho, the problem is with little Grayson...

We got him 2-3 weeks ago from one of my co-workers. Ever since we brought him home he has had problems using the litter box. At first we thought it was nerves and stress from being in a new place, but after about a week with no improvements when going to the bathroom we suspected other reasons. Next up, the vet. We took him there after noticing a small amount of blood in his stool. They said he has a parasite and gave us some antibiotics. They told us to keep him away from the other cats so Grayson got a nice new setup in the bathroom. He has been in there for about a week now getting his meds just like the vet directed. We noticed his stool becoming, for lack of a better word, more turd like and less runny. But still not in the box. We have cleaned the heck out of the tile floors multiple times to try to eliminate any smell and still no luck

His behavior is normal, he eats well, drinks lots, and whenever you go in he leeches any attention he can get. If you sit on the toilet, he will be in your lap within 10 seconds. He loves his head scratched, he purrs like crazy when you do. Hes not showing any behavioral problems, so why the heck wont he go in the box?! We have tried 3 different litters, continuously keep the box clean and no luck. He sometimes uses it, but most of the time doesn't.

Any help or suggestions will be greatly appreciated, as we are both running out of options...  

Is he peeing in the litter box just fine but not pooping in it? If so, he may be a cat who needs two boxes, one for pee and one for poop. He may also be associating the box with painful pooping and things may resolve once he feels better. I would try a second box right away though to see if it solves the problem.

How old is he?  How many cats do you have and how many litter boxes?  Are the boxes covered or uncovered? 

Vball91- I will try a second box tomorrow. Fresh box, fresh litter cant hurt, right?

Stephanie- He is the 7 month DSH. He right now has a box all to him self in the bathroom, it is uncovered. Our other 2 cats have a big covered box and we have never had an issue with either of them using it. But since Grayson is in the bathroom for now he has a box all to himself

Definitely try a second box. My cats are weird. They poop in one box (that's covered) and pee in the other (that's large and open). Strange!

Try a second box and maybe some Cat Attract litter.

Dr. Elsey's Cat Attract Litter and Dr. Elsey's Kitten Attract litter can both be purchased at Petsmart and other special;ty pet stores.  Both are very fine clumping litters,  UNscented except for something that attracts the cats and kittens.  You can also buy the attractant separately and add it to other unscented litter.  Most cats do not like scented litter, and I personally don't like their smell either.  You may look at that little bag of litter selling for $15 and say it can't be worth it, but it IS worth it especially  for training purposes.    I use it for baby kittens once they are old enough to use a clumping litter (i.e. they are beyond the eating it stage -- I use beach sand to start with as it will not hurt them.)  I put a very small box in every corner since kittens tend to go for the corners instinctively.  Once they are trained to the litter, I start moving the boxes gradually until they are all lined up along one wall, then combining two small into one larger box etc.  Early training is very important!  You can't punish them, you just have to make them want to do what YOU want them to do, i.e. make the box(es) as convenient and attrative as possible until they are in the habit of peeing and pooping IN the box.  Obviously your new little one was not trained this way and went wherever the spirit moved him.  So now you have to lure him into the box using attractant.

I just purchased a second box today,we will see how it works. 

Red Top Rescue- I will try that, I had no idea that kind of thing existed. I thought all litter attracted cats! Once he gets the hang of it (If this works), can I start blending in the regular litter, or will I have to stick with this litter forever? We already buy good (and expensive) food to keep them healthy, I don't really want to spend that much money on something that is just for poop. Call me crazy. 

No you should not have to use the Kitten Attract forever.  Just get a good UNSCENTED litter to blend with it, and/or buy the platic container of litter attractant to sprinkle on plain unscented litter when the one bag of Kitten Attract is gone.  You only have to use the attractant for a little while in most cases. 

Since the cat is healthy, I will move this thread to the Behaviour forum where you may get some other suggestions, though I think you have some very good advice so far.