One way to bring it up is in the context of dreams. Do you have dreams (awake or asleep) about having sex with your therapist? If so, telling about the dreams allows it to stay in a sort of "not real" world but still getting to what needs to be said.

I've had these conversations with my T and he is so totally fine and calm - sometimes I want to be really provocative just to get a rise out of him. (no pun intended.) Not that I'd do anything - but just to get him to react. I tell him that too, and he interprets this as me trying to wreck the relationship -- kind of a "get him before he gets me" deal. He seems thrilled that I feel safe enough to have these feelings.

And when I express my embarrassment and confusion and how completely like a cliche I feel, he gets very gentle and says that this does not happen nearly as often as I think it does in therapy and it takes a great deal of courage to talk about it. He said it is a sign of how deeply connected we are. I'm not saying this as good as he says it -- he just has this way of honoring all my feelings for him so it feels better to talk about them instead of avoid them.

From what I've read here, your T will do the same for you. So take a deep breath -- and just say it!