There are various methods. Eastern, Western, or self help? For me, i find that a problem should be properly diagnosed before self-help (evening primrose oil, chinese supplements, etc). I have some menstruation problem as well, and TCM seemed to have helped. If you have not seen a gynae (to rule out anything) then you should start with that first.
Things like hormones, stress level, body weight (health) etc will have effect on menses. So best to check it out properly instead of self-diagnose.