Being that your periods are so abnormal, you're really only going to know if you're pregnant by taking a test. You can get a FREE and confidential test at a pregnancy center. Look one up near you at this site:
The thing to keep in mind, is that anytime you have sex, even if it's "protected", you risk pregnancy and/or STD's.
Breast tenderness could also indicate hormonal problems, and with periods as irregular as yours, that may be the real thing going on with you.
You don't say how old you are - sometimes periods don't become regular until you're older - as opposed to when they first start - say in your early teens.
I also just have to say, it's really important that you reconsider being sexually active before marriage. Have you had a serious talk with your BF about the what-if's? Like what if you are pregnant? Just something I want to throw out there for you to consider....
