How to ask this boy out?

I'm thinking about asking a boy out soon, but I'm scared of what he'll think of me being trans. I'm not out to anyone at school and I don't want to be out yet, and because of that I know he sees me as a girl. And he's said before that he's not gay, which sort of still gives me a chance (since he thinks I'm a girl) but I'm scared that would he would not take the 'im a trans boy' news too well. I don't want coming out to him to mean he starts looking at me different. I know that if I came out well into our relationship he'd probably accept me but it still scares me. (Canada)