Also, sometimes breast soreness with the period is due to dietary things, such as drinking a lot of caffeine. If your diet changed within the last three months, that might have played a part.
Hormones will shift and things change. I initially had it right before my cycle, then I didn't have it at all and now I get it AFTER my cycle is finished (weird). I think it is all normal and just our hormones giving us a hard time.