Hi, Coco. Birth control is also an excellent way to keep your periods under control. Being on birth control does not mean in any way that you should have sex. In fact you should NOT have sex for at least a few years yet. The birth control won't hurt you, and you will always know when your period is due, which is very handy. Blessings - Blu
Birth control can be used for other things, too, so you might find it helpful if you have heavy or difficult periods or bad PMS. Your mom is potentially jumping the gun a bit, but these days, a lot of girls are having sex way too young (younger than you). If you do start it, definitely follow what you seem to be having in mind: wait for sex. It's an emotional thing for a lot of women.
Talk it through with your doctor when she takes you. She can probably help provide insight on whether or not it's the right choice for you.