brown spots on teeth, from retainer???
 

I wore braces 9 years ago, anyway, I still wear my retainer about once or twice a week while I sleep. It is one of those clear retainers, not the wire kind. I think brown spots are developing on 3 of my front teeth from wearing the retainer, because the retainer has worn spots in the same exact places as the spots on my teeth. I haven't had it replaced since I got the braces off 9 years ago. I'm afraid that if I stop wearing it, my teeth will move back to the way they were before. Each time I put the retainer on, it feels tight- like my teeth have moved. But it seems like these brown spots slowly get worse, and they are so ugly on my front teeth. I can tell they are not surface stains, and I take very good care of my teeth- brush and floss everyday. Should I go to an orthodontist to get fitted for a new retainer? And how do I get rid of these stains, will bleaching get rid of them even though they are not on the surface of teeth?