Gender Recently

I have always been one of the guys, from when i could really talk to now. I am twenty years old now and I still love all the same stuff. I work with a few guys and they kind of react to me different sometimes just because Im not the type of girl that really gets dressed up just to go out or go to work. I prefer to be comfy, don't take it the wrong way I don't go looking like a slob, but mostly jeans and a t-shirt. The other day I had to go to the opera for one of my classes, requiring me to dress up. Therefore, I took the time to dress up which i don't hate i just don't prefer. Before heading to the opera I had to stop by work for my check, as I am walking in my manager starts talking to me like a regular customer then realizes it is me. He caught himself then said, " Woah, you look like a girl." I just laughed and nodded. He pointed out that I was wearing heals and I thought to myself, "Do all girls wear heals or what cause I can't really walk in them." I just thought that it was funny that he would say that, because it goes to show that women are expected to dress up and wear heals most days.