It's not just biting, it's ripping! You know, as if he's trying to tear off a bite of tough steak...
I take him off and cover up my boob but then he's trying to take my hand/shirt/duvet back out of the way again so he can go back for more milk. It's actually really sad because it might mean the end of us breastfeeding if he keeps biting, I can't just sit there and take it or I'll have no nipples left! He does genuinely seem to want milk, he just wants to rip my nipple off every minute or so as well 
Any advice?