Bloated tummy

Heyo everybody. First off, I just joined and I'm glad to be here!
Now, to the point. About 2 months ago, my mother and I got a feral kitten. He wasn't tame when we got him, and was coming to us from a colleague of my mother's directly after he was old enough and caught. So we're the first people to ever give him medical treatment or a home.
That being said, obviously the first thing we did when we got him was take him directly to the vet to have him looked at to make sure he had nothing he was going to pass on to our other kitty. Luckily, he was perfectly fine, with just a mild case of worms that was causing his tummy to bloat. They gave us some worming medication and it went away in a week.
That was about 2 months ago, and he's seemed perfectly fine. He's playing, eating, drinking, cuddling, etc. just like any other kitten. BUT, I'm beginning to realize that his tummy is becoming bloated again, but this time more than it was originally, and it feels a bit stiff now when I pick him up or pet him.
Now, do you think that could possibly be the worms? And if so, what would have caused them to come back? Our other cat has no health problems, both of our cats are inside only, we change his litter box very often, he finished his worming treatment..and we're not sure what it could be.
At the moment, we don't have the money to get him into the vet right away, but are planning to take him in next week. In the meantime I'd love some insight as to what this might be, and if it's anything serious. I get so worried about my baby.

(Just because I love showing him off, here's a picture of him. His name's Axel.)

Thank you ahead of time for the help! This is our first feral kitten, so we're not used to our kitties having many health problems or anything. Sorry if I sound clueless!

- Portia

Welcome to TCS Portia.

Firstly, it can sometimes take more than one dose to eliminate worms, depending on the type of worm he had.

I would be very concerned if his tummy is bloated and hard. I know you say you can't afford the vet until next week, but I honestly don't think you should wait that long. Maybe you could work out some kind of payment with the vet office. I'd especially be worried as whatever is wrong with him could also affect your other cat if they are using the same litter box(es) or sharing eating bowls.

I don't want to alarm you, but please try to get him to the vet as soon as you possibly can. I don't think you should wait until next week.

Well, as far as we know they haven't been using the same litter box or eating from the same bowl. They have separate boxes and food dishes (and food) until we're certain that he's healthy, and he seems to prefer not sharing with our older cat anyways. So unless it's a different story behind our backs, they aren't sharing anything like that (Lucy doesn't even want anything to do with the poor boy)
Now that I'm petting him and picking him up now, it really doesn't feel stiff anymore. Still bloated, but not stiff. Although thats not to say it can't come back.
We may be able to work out a payment arrangement with the vet's office and get him in tomorrow morning. I'll have to talk to mom about it. Like I said, he's not ACTING strange. He's eating, drinking, pooping, etc. all like he should. And he's still playing and cuddling and acting as if nothing in the world is wrong. But nevertheless, I'll look into setting up an appointment for him tomorrow morning.

UPDATE: Okay, we're making an appointment for him tomorrow morning. I'll update tomorrow.