Suggest Treatment For Irregular Menstrual Periods

Hi, I'm a 25 yr old female in the Navy I've been having severe problems with my menstrual period over the last 6 yrs. I've been to numerous doctors because I will go over a yr without a cycle and when it does come it last for months. The shortest its on is maybe 2 months..I'm currently on my cycle and tomorrow will make 6 months. I've tried everything from birth control to vinegar....nothing works. I'm weak, cramed and tired. All the doctors say its normal but this can't be. I'm in serious pain. Please Help