Help - cat emotional problems!!

This has happened in the past, but we got through it but I am wondering what else we can do -

Our 1 year old cat Percial occasionally (has happened 2 times before this one) just freaks out. He starts compulsivlly grooming his front paws and chest, he tries to sit in his litter box and he breaths heavy, somtimes panting.

The first time we took him to the vet and the vet determined he was teething (you could actually see 2 fangs on each side!) The vet said some cats when they are scared etc, seek out small enclosed spaces (ie covered litter box)
The seond time we put him in his room (where he eats, etc) and closed the door with a Feliway plug in. We took the lid off his litter box so he wouldn't want to sit in it. I have looked for a cat cave thing, but he is too big to fit in any that I have seen (we got one and wound up giving it to our other, smaller cat)
These episodes seem to pass after a while of being shut in his quiet room with the curtains drawn. We can't seem to find any specific trigger (other than the teething the first time)

I just am wondering if there's anything else we can do to get him through these things. We took him for his annual physical last month and asked about his behavioral problems (aggressiveness, not knowing limits, and such) and the vet said that sometimes kittens taken away from their mothers too soon have problems. (we found abandoned at 5 weeks)

I have tried to find a larger cat cave for him to sit in as an alternative to his ltter box, but can't seem to find one. I thought about a dog thing, but we have a small house and can't really have a dog house sitting around. (space issue)

Any help or advice would be great - thanks!!

maybe he would like to sit in his carrier with door open and a cussion in there.

how about a cardboard box with a comfy blanket inside?

ikea has a really cute cat/dog tent. These are the dimensions:

Product dimensions
Width: 19 "
Depth: 19 "
Height: 15 ¾ "

to look at a picture, go to ikea.com, choose your country, for the pets, pet bedding. I really want to get one, but it's only available in the stores, none of which are in my immediate area.

I found a larger-sized cat cave at Walmart. It's kind of shoddy construction, but it is large enough for a good-sized cat.

Keep in mind, too, that your cat is just a "kid" yet at one year. A "teenager" .... and you know what they're like!!

Thanks to everyone. I'll check walmart and ikea. The main thing we don't like about these 'episodes' is the sitting in the litter box. It is just... ewww.. Despite the fact that as soon as I saw him doing it, I completely changed it so it is clean, we just don't want him to get used to sitting in the litter box.

He is doing better tonight. He has eaten, not gone potty yet (good since he has been going back into the litter box sometimes) Still a bit jumpy, but he has come back into the living room (with frequent romps back to his feliway soaked room) He played a little bit (not his normal play activity, but he pawed at the feather a little) So hopefully after spending a night in his room (with the feliway plug in) He'll feel better in the morning.

Now is just the task of training him to use another (more sanitary) comfy hiding place.
Thanks again!!