My greatest fear

I've been a devout heterosexual all my life. Within the last few years for some reason I have been having fantasies about and the desire to suck another man's cock. Not just any cock, I have a fairly specific size and shape of cock that I want to suck. Also the person whose cock I suck has to be very patient and understanding that this is something that I would have to slowly work up to. I don't think that I could just pull someone's pants down and wrap my lips around their hard cock.These are very vivid and conscious fantasies. So realistic that I can see and almost feel my mouth around their cock. I can almost feel that rigid shaft sliding in and out of my mouth and the head gliding over my tongue. I can feel their cock pulsating and jerking as it explodes in my mouth. I can feel and taste their cum as it flows across my tongue and fills my mouth. I actually get an erection and have to masturbate every time I have these fantasies.
I've been in touch with a few different people. They seemed to be fairly understanding, but about the time we set up a meeting I chicken out. This would be a life changing event and I am thoroughly frightened by it, but at the same time I am completely aroused by it. I don't know how to handle this and I can't seem to find anyone to talk this through with.