My last period started on the 14th of August and was normal for me. Today is 12 days later. My boyfriend and I are sexually active (but we ALWAYS use condoms, we're very careful and we've never had one break or slip) and have had sex on the 20th & 24th of August. Tonight when I was taking off my shirt, my breasts felt weird and when I checked them, they're kinda tender. Usually they only do that for the 4-5 days before my period. And the right one has a weird lump or my gland is swollen kind of on top and nearer to my armpit.

I'm just worried. I don't think it would be pregnancy since I just had a full period and we practice safe sex. Any ideas on what else it could be?