Getting on birth control need help choosing

Hello ladies I have a doctors appointment in June , I know it’s far because the doctors are the best I town . But anyways, I want to get in birth control but don’t wanna gain weight and don’t know which one to choose from . I heard something about a mi I pill ? And right now my periods are all over the place I’m 13 days late this month not pregnant I’ve Token about 5 test all negative so I’m going with a no . And my hormones are all over . I just need some advice.