Another Plateau! Need motivation :)

I have been using MFP for almost 9 months and lost 35 lbs! Great, I know! But here is my struggle... I lost my first 15-20 pounds pretty easily and then, at 3-4 months in, I hit a plateau for at least a month where I did not lose any weight and I got very discouraged and almost quit. I reevaluated my diet and gave it one last push and finally began to see progress again. Now, 3-4 months after my last plateau, I have hit another one. It has been almost a month and I haven't lost a single pound (Actually I have gained a little). I am trying to net 1200 calories per day, usually eating 1800-2000 and burning off 600-800 with running and weight-lifting. Am I doing something wrong or do I need to adjust something else? Help! I am getting really discouraged again :( My goal is to lose 50 more pounds to be at a healthy BMI.