Why are they getting bigger!?

Hi there, I'll start off with some basic facts. I'm a 21 year old female. I have been having unprotected sex with one partner. I do drink. I've been gaining weight lately...a lot. Two pant sizes within a month or so. My breast have doubled, almost tripled size. Before my last period I took like 10 pregnancy test because I had symtoms but all were negative. My period was very heavy with large blood clots for the first few days then very light, almost nonexistent for 8 days. My breast haven't stopped growing and are still so sore. All of my friends that are mothers are convinced that I'm pregnant because of my body changes. My period is due soon so I took a hpt and got a negative result. What's going on here!?