I got a 6 week old kitten last week form a friend and I noticed that since I've had him he's really become fat. I have been feeding him kitten food three times a day, he has been urinating and pooping regularly, and he is energetic and playful. When I got him he was fine now I am worried that I did something wrong, I would really like some help if anyone knows what is wrong with him. It might be worms but I am not sure. I think I will make an appointment with a vet today if I have to.

Yes, a vet check is definitely in order.

Is he fat? Or bloated?

I agree with WG, time for a vet check.