Help!!

Pamela
My baby is 6 wks old and for the past week or so every time I feed him he looks so uncomfortable and grunts and looks like he's trying to poop. He squirms so much and starts to cry that he doesn't always finish his bottle. I tried giving him gripe water and it has helped alittle bit but this seems to happen only when I try to feed him. Anyone else going through this??