I don't know what's going on!

I thought I stared my period on the first. But it was never heavy and it would start and stop. I had breast pain but didn't think anything of it until now because it hasn't gone away and it's just gotten worse. My aureolas have gotten bigger along with my boobs themselves. My boyfriend also noticed the difference too!  In the last few days I've felt nauseous on and off as well. I took a test late in the day today and it came back negative. I just don't know what's going on. If I'm not pregnant then something is really wrong.