Milk supply decreasing

All of a sudden my milk supply has decreased. I'm 3 weeks pp, they used to fill up to the point where they would leak like crazy after about 5 hours. I used to get 3-4oz on each side every time I pumped, plus whatever my son got during feedings. About 2 days ago my supply has completely decreased. I'm only getting 2oz if I'm lucky out of one side and only an ounce on the other. I'm pumping every 2-3 hours plus feedings and it's not increasing. I also started getting weird pains in my breasts. It's like a tingling but it's painful and lasts about 39 seconds. And it seems like the pain is in milk ducts because it's several spots on my breast that would hurt. Anyone have this problem? Any advice? I am EBF and I'm afraid I'm going to lose my supply