frequent eating, help

I exclusively pump. My son is stuck in this cycle where he eats only 2oz every hour-hour and a half. He eats what he's supposed to in a 24 hour period, but I'm CONSTANTLY feeding him. I've tried faster flow nipples, but it just ends up all over him instead of in his mouth. I've tried waiting a little longer so he'll eat more at once but he flips out screaming and crying until I feed him. Any ideas on how to get him to eat more at once so I'm not feeding him all day?