My boobs have been sore, now I'm spotting..

My boobs have been sore for almost a month now since my last period. I just got my period Saturday(3 days earlier than it should of come) which was extremely heavy (really abnormal for me) and now today is Tuesday-I started spotting and have almost no bleeding whatsoever. Does this happen for anyone else? It's pretty unlikely that I'm pregnant, and every test I've ever taken in the past has been negative. I also have Celiac Disease and was wondering if this could be a factor of irregular periods?... Or are my boobs just possibly getting bigger? (I'm only 25)