Suddenly have sore breasts?

[shellideaks]

I'm exclusively pumping for DS2 and haven't really had any problems with it so far. In the middle of the night last night, I woke up cos my breasts were really hurting. It kept me awake for a lot of the night and is still there this morning.

I've pumped as usual (which also hurt a lot) but I'm not sure what's wrong. Its both breasts that hurt, no nipple pain, just the actual breast tissue. It's like a sharp stabbing pain. Does anyone know what it is?