This is what I did and what worked for me:
I noticed that soon after my milk came in my baby started looking uncomfortable during feedings. Just squirmy and pulling off with some crying, but he would always try to go back on. I couldn't get him to nurse for very long and feedings were getting shorter. By 3 wks he would have a few gulps and then cry and not even bother to finish nursing. He never spit up at all. If I caught him just as he was waking up I could get a bit more in him before he started to react. He seemed to nurse better during the night as if he was too drowsy to let it bother him. I had had a problem with latch with my first son so I went to see an LC to make sure that wasn't the problem here, just in case though I didn't think it was. Regardless, I needed some help. He was just barely making the daily diaper requirements. My LC suggested that it could be a milk allergy or reflux. I stopped all dairy entirely, even traces of. It took about 2 weeks to notice a difference but things got better. It seemed that the milk products were what was causing the reflux. At 10 weeks he is nursing through entire feedings without a problem.