@righteousbyfaith I usually wear work clothes that is flattering but not bugging tight.
My GF met me through work but she had no idea what I looked like underneath the work clothes until she saw me in a tight tee shirt at a social function unrelated to work. She knew I was slim and fit but had no idea how much.
That tight tee shirt was a big part of closing the deal for her. She wants to take me to the beach since I don't go outside much to show my body. She wants me to go shirtless at the beach more than I do.
But that's just my experience. You already have a gf. Take my story for what you will. I say wear what's comfortable for you, mentally and physically.