My very first session with my first therapist was with me presenting as male. The session went well, if we call 'well' my completely falling apart with 50 years of repressed self exploding all over the office.

For my second session, I wore my jeans, size 8, and a teal lightweight long sleeve turtleneck, with the usual padded undergarments, and a nice Calvin Klein jacket. When he came into the waiting area calling my male name he completely missed me. I stood, he did a little double-take, "Oh, there you are. This way..." and I was off to my second session. I know what I looked like... Brrrr...
He did ask me why I was dressed for the session. I mentioned that he HAD said this was a safe space at the start of the first session, and that I felt better and thought I might communicate better as myself. Then we dove in..
So, yes, you can go as yourself. It's a safe space, and I guarantee that the doctor has already seen it all. If it helps you to feel more comfortable, or to communicate better, then by all means, do it.