Ladies, I need advice on my appearance and how my girlfriend could react?

I have had a little bit of trouble with my weight over the last few years so I have tried diets and workouts to help this problem. In the meantime I purchased those slimming compression shirts to wear as an undershirt. It does make me look much slimmer, still I look stocky but it at least hides the gut and moobs that once showed without the undershirt. It also gives me a little confidence that I am not as fat as I once looked. Here is the problem; I have been wearing these slim shirts under my dress shirts which is fine for work or a date. My new gf and I went to a baseball game last weekend and she asked why I was wearing an undershirt since it was really hot outside. She could see it under my jersey tee shirt. Now I am paranoid that she is going to be weirded out if we get intimate and my shirt happens to come off and she sees that I have been wearing this undershirt to hide my fat. I am wearing the undershirts so she doesn’t think I look like a beached whale. So ladies, would you find it weird if your bf wore an undershirt that hides his belly fat? A little advice to make sure this isn’t awkward.