Enlarged breasts?

Ok so, I'm 19 and I've been having sore breasts for a few days now and I feel like they've gotten a bit bigger. The thing is, my period isn't for until another week so I'm not sure why I'm feeling this way. My partner and I have had sex unprotected twice in the last month, but I currently have an IUD and he pulled out both times. I don't have any pregnancy type symptoms, but I can't help but feel anxious about the idea of being pregnant. Should I be worried?