infertility phobia/ LONG POST

I'm a 20 y/o and I've never really tried to conceive but things have happened and I haven't ended up pregnant. LET ME BE CLEAR I'm not saying everytime you have sex in your fertile period you'll get pregnant, but it's happened about three times and one time I had seamen in me almost my whole fertile period. I also understand that seaman can die after a couple of days and that this app is an app and can be very accurate yes but could be a couple of days off or so. ( not that it is or isn't) 
I'm 20 almost 21 and I have this huge fear of being infertile because when I was 16 I had anorexia and I lost my period for 9 months and I know that isn't good not horrible but not good. I also because of the anorexia I drank a shit ton of diet sodas again not great for the body. But because of those things I have a fear of being infertile because I haven't gotten pregnant the couple of times I could have. LET ME BE CLEAR my boyfriend and I aren't trying and I know that this can take time. But with this fear of being infertile. I also want to have a. Any in the worst way. I wanted one before this fear came to life. It came to life because I was like wait why am I not pregnant when I should be because it was my most fertile day and there was a lot of seamen... now for the past six months to a year when ever I get my period I bawl because I want a baby because I'm afraid I'm infertile and because it's my period.... I'm almost 21 why am I thinking this way why do I want a baby so badly at the age of 21 why? The re isn't a day where I don't think about having a baby and then thinking about being infertile and it breaking me down. My boyfriend feels bad for wanting to use a condom because of how I feel. That's so fucked up on so many levels... I don't know what to do anymore...