Do I have fertility problems ??

Why don’t I ever get pregnant when I have unprotected sex ? Sex ed always made me think that even if you had unprotected sex one time you will get pregnant . I’ve had unprotected sex numerous times and have been came in (with the same partner I’m not doing it with a bunch of different people) and I’ve never gotten pregnant . I’m 21 and no major health issues so I’m not sure why ? I feel like I’m infertile but no one believes me when I say that. I won’t even take plan b because I know I won’t end up pregnant it just doesn’t happen for me. I’m not trying to get pregnant either I just feel like I have been worrying about an unplanned pregnancy for no reason . I’m also not on birth control and still no baby. The rest of my family pops out kids like it’s going out of style (nearly all the pregnancies were unplanned) and there’s me who is like a barren desert.

Edit:someone asked about my periods, they are irregular I get them about every two and a half weeks !