It might be worth trying a drastic change in how you feed him. If you normally feed with you sitting then try lying down - maybe even lying on your back. Something so that he has to stop and think "how do i get to this boob".
You can exclude/verify the teething issue by giving him a dose of panadol half an hour before a feed and seeing if it makes him better behaved. If it does then you can't keep constantly dosing, but you know it should be better eventually!