Why can't I sit on his face?

B loves going down on me, and I love that he loves to do it. Our sexual realtionship started with him begging to go down on me and I've been addicted to his tongue ever since. He is simply a master of this craft. We can be sitting on the couch watching tv and he will turn to me and ask if he can lick my pussy. Sometimes I turn him down just to make him beg and let me tell you, there is nothing sexier than a man begging to go down on you.

The "problem" is this: I cannot bring myself to straddle his face. He has been asking me for months to do this. I don't know if maybe I am too uncomfortable with myself, or maybe I am afraid I will suffocate him? Its not that I don't think I will enjoy it, there is just something that stops me every time he asks.

Last night, with a little liquid courage I got as close as I ever have to attempting this act. B was sitting on the floor in front of the couch and I stood in front of him, still not sure at this point that I could do it, but I put one knee over his shoulder, rested it on the couch and lowered myself onto him. It felt great, but for some reason I just couldn't let myself enjoy it.

Afterward, he told me how happy he was that I finally did it and how much he enjoyed it. I have a feeling this wasn't the last time I will try and hopefully I will be able to toss my fears aside and enjoy.