My last period started on the 14th of August and was normal for me. Today is 13 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 had sex on the 20th & 24th of August. Yesterday when I was taking off my shirt, my breasts felt weird and when I checked them, they were kinda tender. Usually they only do that for the 4-5 days before my period. And the right one had a weird lump or my gland was swollen kind of on top and nearer to my armpit.

Today they're still tender but less than yesterday but my gland still feels weird...

I'm just worried. I don't think it would be pregnancy since I just had a full period and we practice safe sex. Could it be because of ovulation even though it's never happened before? I'm only 18 so I guess my body could just be developing or something... Any ideas on what it could be?