Constipation (Recently diagnosed with Diabetes)

Hey there,
my newly diagnosed cat named Kitty (16 years old in May), has just started on wet canned food Monday and is on amoxicillin and nsaids daily for 2 weeks. Also, started on vetsulin on Tuesday. I've noticed he hasn't had a bowel movement since Monday, I guess he has been under high stress going to the vet for the first time ever on Monday plus the new diet...what can I do to help Kitty finally have a BM? thanks.