Hi S.. I understand how frustrating it is when your little one suddenly decides not to cooperate. Trying to get them to latch on while they're frantically squirming the other way will wear you out. I would say that there are a few things worth checking out before you throw in the towel on nursing.
Has anything in your diet changed? Any new medications? It could be that there is a different flavor or something to your milk. (My baby lets me know I've eaten something she doesn't like by biting my nipple!)
Could he have an ear infection? It can hurt to nurse with an ear infection.
Is he teething? Same issue - nursing can cause ear pain when teething.
Is he just too interested in what's going on? Nursing typically puts baby in a position where they can't see what's happening. Right now, my baby fights me like crazy because hunger is secondary to her curiousity. You could try a different position or go into another room where it's quiet.
Lastly, are his table foods making him gassy? If so, it might hurt his belly to lay down and nurse. Try mylicon drops and tummy rubs if he seems gassy. You can also try to nurse with him sitting up (sit him beside you on the couch facing you - you can put a pillow under him or even sit him straddling your leg if his mouth doesn't easily reach your breast).
Until you get it figured out - I would keep on pumping to protect the supply you have and drink plenty of water to try to boost it a little. Good luck!