Stuck?

Just wondering how many people have hit a plateau? Ive lost 20 lbs since July of 2012 and have 15 to go (doctors orders) and Im stuck. How do you personally kick start your metabolism to continue to loose weight healthy? Or is this not a problem for you? Just wondering how many people feel like me. I haven't lost any weight for about a month yet I am maintaining the weight loss well. How long can this go on... Help, thoughts?