...Tell him beforehand.
If you really like him, then you should be able to trust him with any personal secrets that you might have. And if he really likes you like he seems to, then they shouldn't even bother him at all; besides being bothered with concern about you of course. I think that he can just look past it. He can see the pain that you have been through, and can just realize that he is making you happy by being with you and by, more importantly, accepting you for the person that you are. :)