What Are These Tummy Pains?

Nearly every time mummy feeds me, I get pains in my tummy. I don't know what they are but they make me cry. But if someone pats and rubs my back, I can do a big burp and the pain goes away. Sometimes I even do a big fluff. And sometimes I even spit a bit of milk back up. Does that mean I drank too much? Maybe I am a greedy guts sometimes.