I want to start using birth control

I've heard many great things about birth control. that your skin clears, less cramps, lighter flow and best of all pregnancy scares are unlikely!! But I've also heard you gain weight which doesn't make me too happy:(. Also, I'm not sure how to convince my mom into letting me use it. I don't want her to know I'm having sex, I've already said that I wanted my period to be lighter and she brushed it off and told me i can deal. Someone help me figure out on what to say and if I should even bother with it?!