Help. I think I need assistance. I didn't think I had any pro...

Help. I think I need assistance. I didn't think I had any problems with Mirena, but now I am not so sure. I have had my Mirena in since March of 2003. I have had no problems to speak of - next to no periods, light spotting - things have been great. I had always been overweight. I had weight loss surgery (Duodenal Switch) in December of 2007 and have lost 100 lbs. I've seen my gynecologist during this time and things are fine. Recently, I'd say in the past five months or so - I bleed for no reason. I have no pain and no side effects to speak of other than this bleeding. It comes and goes with no regularity whatsoever. I am 46 years old. What should my next step be?