Could Sore Breasts Be Due To PMS?

Hi, I'd really appreciate some help because I'm really scared. I'm 20 years old and still a virgin. My boyfriend and I have messed around, but we have never taken our underwear off. He has never ejaculated anywhere near my vaginal area. My last period ended January 28, so I'm not due for my next one for awhile. For the last 3 days, my breasts have been really sore. I have heard that this is a symptom of upcoming menstruation, but this have never happened to me before. Could I be pregnant?