Help!

Ok so I'm planning on getting on birth control because my period is always messed up. Like I'll miss 5 periods then bleed really heavy for 2 weeks. I'm 16 and I've had my period for 5 years. I'm nervous about getting on a pill, but it just got too painful and is interfering with my life. I would like a pill that would also help me gain some weight and make my boobs grow a bit, because I try to gain weight but can't on my own (I'm tiny please don't judge me) what pill would you guys suggest me asking for?