Hello iam 15 year old and I need help with medical problem I havenst seen my period since june?

Are you sexually active ?that would be my first question and have you had any problems the backache could be pms is the vaginal discharge could be pregnancy related if not question is are you having may be a sexual vaginal infection you might want to get a test and see if theres a positive test that would be the first thing to check out if not go to the dr and see what else it might be