M.C.
I had a very similar problem when my son was about 3 months old. He had been a great nurser up until that point and then he would scream during every feeding. It is really upsetting! I finally figured out that he would get upset when my milk wasn't flowing fast enough. He would pull off after only 5 min. or so and scream. It got to the point that he lost weight and my milk supply dropped. Once I figured it out I got a pump, and I would pump and then nurse him and then as soon as he started getting fussy I would give him the bottle of pumped milk. Kinda sounds backwards, but it kept my milk supply up and kept him fed. Once he started getting good meals at each feeding, he stopped fussing. I would suggest you call a local le leche league if you need more help. Hope this helps!!