I'm so insecure with my body an apperance that it affects me getting in a relationship in general! I find myself repulsive. I have stretch marks, cellulite, bad teeth, my ears stick out, I'm losing my hair, blah blah blah. The thing is though, as much as I resent my own looks, I don't care about the flaws of others at all.
If the 2 of you have been together as long as you have, I do truly think he will be fine with you. If you sit down and have a proper one on one discussion about how you feel, and hear how he feels, you might begin to get over your fear. It is not something that you can get past overnight, and it will take his help to make you feel more confident. He should respect you enough to know your limits, and not try to push you into anything that is out of your confort zone, that should be something you should decide to do yourself.
I honestly can be more help than that though sorry, especially as I'm having an extreme ugly day at the moment, my advice is probably irrelevant!