Internalization

I don't think being trans is something to be ashamed of, but I feel ashamed.
I had though, until just this last week that I did pretty well in terms of self acceptance, but I'm coming to realize I still have quite a way to go.
I started seeing a guy recently and things are going very well between us. 
I like him rather a lot, probably more than I should given how short a time it's been, and he's never done anything to make me feel even slightly self conscious about who I am.
But I am feeling self conscious.
It came as something of a surprise to find that while I'd like to think I'm very comfortable with who I am around friends, when it comes to someone I'm having sex with, I catch myself quite deliberately avoiding conversations that address my biological past.
There's no good reason for this, after all I'm 99 percent sure he's noticed that fact that I have a penis, but I still find it hard to talk about. 

I'm afraid that if I draw attention to my being trans, he'll suddenly stop seeing me as a woman and I'll no longer be desirable.
This is a real problem.
Not only does it make me feel very vulnerable, but it means I loose one of the most valuable things in a relationship, having someone to comfort you when you're feeling scared and alone.
I'm realizing that until I can find some way past my own sense that being transgendered is something shameful, something that's wrong with me and makes me undesirable, it's going to be really hard for me to accept that another person genuinely want's to be romantically involved with me. 

I guess it's the same for anyone who's considered undesirable by the narrow minded norms of beauty, whether due to disability, body shape or any other reason.