Need help, or advice.

I'm currently having my period anywhere from one to two weeks apart from each other. I'm going to the doctor next week to have it checked out because this is concerning. This has been going on for almost a year now. I was on birth control for about 3 months this year (January to march) and I was still having the same thing happen to me. Previously I was not a birth control since December 2014. And this has been an ongoing battle. Since December 2014 I have gained quite a bit of weight, but I can never seem to lose it. I'm at a stand still. I don't know what to do. :( I'm scared, and hopeless.