My girlfriend is trans (MtF), and in my experience, it is actually really important to dare to openly talk about these issues. At first I did not really dare bring up my questions and the things I was uncertain about or struggled with, as I was so afraid that I would hurt her in any way. It is my experience now that if you keep it close to yourself, you can talk about these issues without hurting the other (or inducing their dysphoria). For example, you could tell your boyfriend that you feel sad about the prospect of (maybe) not being able to give him pleasure, because it is something you find very valuable when having sex with somebody. You could add that at the same time you find it very important to respect his limits. You could make it clear that it is something that YOU experience as a problem, and that the solution is not necessarily that he should do something he doesn't want to. I think this way, you can talk about what bothers you while at the same time respecting his bodily integrity. So I don't agree with people who say that you should not bring this up! These issues are sensitive, true, but if you are in a relationship you should be able to talk about intimate things (in a respectful manner).
