I don’t understand why I can’t get pregnant...

Why is it that women who use drugs are more likely to get pregnant than me... in the county I live I see many of young women who have been users and always get pregnant.... some friends of mine have gotten pregnant without any issue and I hate to feel some type of way about it. Why is it so hard for me.... I’m tired of crying, praying to god to please let me be a mom, I’m tired of negative tests. I’m tired of breaking my heart and seeing my partner feel awful because I can’t stop crying.