I'm 2 months post op...

I just ate a piece of baked breaded chicken about 3-4oz with a lemon sauce not paying attention I ate it in about 15 min

I'm concerned because it went down easy, and not in any pain, usually when I eat that much that quickly I get a strong pain in my upper abdomen... Can my stomach have stretched already?

No your stomach won't stretch that easily. You were just fortunate.

That's normal. Our stomachs are supposed to stretch just a litle bit in the immediate post-op period. Your stomach isn't doing anything that it isn't supposed to be doing.