I get this every pregnancy, I hate it... It is always worse if I am not wearing a bra, I find if I put my bra on, and have it really supportive, it helps to take the pressure off a bit...ah, the joys of being heavily pregnant

I find I spend a bit of time wandering around with my arm under my boobs holding them up! haha quite unconsciously, just to make me feel a bit better (not in public lol)