could I be infertile?

I'm almost 23, lost my virginity at 15 and have had a good amount of partners. I'd say about 80% unprotected. most guys pulled out but my ex a year ago came inside me every time for almost 2 months (never told me) and so far I've not gotten pregnant. I'm on birth control now and I was for a short time in high school, and yes I know it was very risky behavior... I'm not trying to have kids anytime soon but I'm wondering how the hell I got so "lucky"?? I don't necessarily want/need to take a fertility test I'm just curious if anyone else has had this happen. as I've said, I've been very sexually active with over 30 men