Joe is right. Confidence is the most important part. Men find it very sexy and a turn on when you are comfortable in your own skin.
Also (and this may get me into trouble) a lot of the time men don't notice things that women do. I've had instances where I have chopped off my hair dyed it a completely different colour and my sig. other has said "you look a little different..did you do anything?"
So I guess what I am saying is it may be a non issue for your boyfriend..
Also women never get the opportunity to "sneak preview" a man's package before they do the deed. A least men have a "kind of" idea of the size of a woman's breasts.