you could try something, to boost your confidence:

when you enter the gym, pretend like it's your place. not in the way of "i am the master here, obey me," but in the way that this is your playground, your favorite place in the world, you keep it clean, and make sure everyone is having a good time. you could even rerack weights left out (it's still exercise!)

when i'm in my neighborhood playground & park where i work out, i routinely pickup trash because i'll be back the next day, and it feels good. sometimes i even get a thank you from other park visitors.

it's not about you and the girls notice everything.