DS is 6mo and has always 'scrabbled' at my chest/neck when feeding, especially at the start of feeds. At first I put this down to frustration as he had a TT that we didn't manage to get snipped til he was 6 weeks and feeding was slow and difficult until then.
But he carried on, and this is now turning into pinching, thumping my neck, flailing, grabbing glasses... making feeding somewhat less relaxed than I would like. I have tried beads round my neck for him to hold but to no avail - he sometimes grabs them but continues the bashing. Its got worse this week as he has learned to clap hands - and tries to do it with one hand against my face when feeding 
My 'tactic' has previously been to hold his arm down with a finger inside his sleeve but this is becoming ineffective and he struggles against it now. He also will sometimes settle for holding the thumb from my opposite hand, but that means feeding is a two-handed job making MNing impossible
Anyone else had a baby that does this, or know of anything that chills them out at the breast a bit?