Women getting pregnant while on birth control 😠😭

Every single one of my closest cousins got pregnant accidentally. I know for a fact that 3 of them were on birth control when it happened and 2 got abortions. I always see everyone complaining about people around them getting pregnant and not them... I don't wanna complain like everyone else but I just really don't understand how some women can get pregnant while they are on birth control. Us here ttc get off birth control with the hope that we'll get pregnant right away but it takes forever. its just so frustrating. All I want to do is be a mother. I feel like being a mother is my calling, what I'm here on this earth to do. If we have infertility problems I think that might really be the worst thing that could ever happen to me.