Extreme breast pain!

So I tend to get tender breast just before a period but over the last 3 months I’ve had constant pain and its getting worse. I’ve gone from a D cup to a FF in 3 weeks and I literally cannot move without being in pain. It feels like my boobs have just been pumped fully of liquid! I’ve been to the doctors several times and they don’t seem to know what’s wrong - cancer has been ruled out but I was wondering if anyone else had experience something similar or has any advice