No period but not pregnant?

Jade

Hi! So I'm not sure what to do or think... I have not had my period since the beginning of June and I know your thinking "oh your pregnant" but nope. I've taken 3 at home tests all of which have come up negative and i have not shown ANY signs of a pregnancy. I also was on birth control when getting intimate plus the use of a condom, I made a doctors appt for later this month but I was hoping someone here might have some insight as to why my period has been gone for the last 2 and a half months..