Could he be teething if he's shoving his hand in his mouth. I know this is pretty normal to stick hands in their mouth but it may be associated with teething and that can cause fussiness with feeding.
Also my son went through something like this. Started at about 3.5 months. During the day he was screaming with his feeds, but not the night and morning feeds I was doing in our bedroom. He also has reflux and had also just had a major mouth operation - he has a cleft lip and palate - so I figured lots of reasons to scream with feeds. I was using various forms of pain relief that we'd been given post op and mylanta. Eventually someone told me their son got really fussy with feeding at about 4 months and they couldn't feed in public. I didn't think the kind of screaming he was doing could just be behavioural, but I tried feeding him in our bedroom with the lights off and curtains closed and it made an amazing difference. He would all of a sudden take his feeds with only a little fuss.

Big hugs. It was absolutely awful trying to feed him and have him screaming like that. I felt helpless, on the verge of tears, while trying to stay calm so that he'd calm down. It may not be the same thing - cause he was happy as larry when I wasn't feeding him - but I know how difficult it is.