Screaming in pain

Hey everyone, looking for some help. My little guy is 3 months old and about an hour or two after almost every night feed he wakes up screaming and crying instantly with real tears like he is in pain and it seems no matter what I do he can’t calm down for a good 10-15 minutes where he falls back asleep. I make sure I don’t lay him down for 20 minutes after he eats and he usually gets one burp out. I lay him on his back to sleep. He often brings his legs up in the air too when he’s crying but not always . Any advice would be great on what this is or what i should do