Self love may go a long way here in helping you get your "sexy back." Allow you to get yourself off first while dealing with the mental negativity might help you overcome the thoughts you are having while he is trying.
It is only a suggestion, but it worked for me. In the past, with my ex, I would joke about it a lot as well... he would make attempts, I would respond with something like, "oohhh I don't know, there is a rumor going on around here that you have herpes, what kind of a girl do you think I am?"
Herpes is really not that serious, it is kinda funny if you think about it. It is nothing much different than Acne but shows up in the least of desired areas. It is not NEARLY as bad as education pictures suggest. Have you ever googled a "small house fire?" One of the first pictures is an entire house burning down... when you google Herpes outbreak, you practically see the worst case scenario and OMG, is that penis about to fall off!?!?!
Make it funny, make it light, make it not so serious and you will see the people around you do the same. Your energy rubs off on everybody but affects you the most. So, make it funny to yourself, get yourself off...and slap the shit out of yourself if you need to. I highly doubt you would allow ANYBODY else talk to you the way you do. Seriously.