I was in the same situation, and it takes some time before you feel comfortable with it, just explain to him what you are feeling, and if he truely has no problem with how you look, he will keep giving you emotional support...and soon you will feel better about it and won't give it a second thought, also some guys like curves!!! relax and enjoy yourself .
Now for me it took almost a year!!! and now i don't even think twice!!