Hi, Deb and welcome!
I'm sorry your new, furry addition has a swollen belly. The usual causes for this are intestinal parasites, gas, or constipation. You said he's going to the bathroom alright, so I assume he's not constipated, which is great, but since he was wormed a while ago, he might need another worming. Typically, the worming treatment is given a few weeks apart, so the best thing to do, would be to bring him to his vet for a complete check up and a diagnosis as to the swollen belly. If he needs to be wormed, the vet will give him the medication and then, might tell you to repeat it in 2-3 weeks.
For the moment, if he is eating, drinking, eliminating and playing/acting normally, that's great, but try to get him in to see the vet tomorrow, if possible.
I hope all will be well with your little guy!
I hope this helped, but please let me know if you have any other questions.
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