Keep your shirt on during sex. I do that most of the time because of other issues and my own comfort level. Guys generally will not care. They are happy to be getting action. So what if you want to wear a shirt, they are not thinking w/ the correct head anyway.

Can you go to a breast prosthetic shop. Purchase something that will help fill out both cups of a bra a little better.

I've seen stick on boobs at bra and undie shops. Madenform and Playtex and such. It is to be warn under a shirt or bathing suit. It is squishy and feels like and looks like a normal breast. It is a gel like substance and can be washed and re worn. They are made to even out the size or add to the size if you are not blessed in that area.