Does anyone else’s baby claw/pinch them while eating?

My baby is 4 months old and has recently started exploring with his hands. He has started grabbing my nipples and twisting, clawing me, and grabbing handfuls of my skin really hard, all while he eats. I’ve started putting mittens on while breastfeeding him. What am I supposed to do? He’s way too young to understand what he’s doing and I guess he’s just exploring using his hands? But he’s hurting me and making breastfeeding really unpleasant!