3 wks baby suddenly refusing one breast

Sa

Yesterday my baby started fussing and refusing one breast out of nowhere. We’ve had no problems with this before. I pumped that one the rest of the day and tried it again this morning. She was still fussing and didn’t want that one again but would feed on the other side. Plenty of milk was coming out when I would hand express and I pumped after and got 3 ounces in 8 minutes. I don’t know what’s wrong. Calling lactation consultant when they open. Does anyone else have experience with this? I don’t think my let down was too strong either.