I read your post and I have the SAME kind of compulsion to perform oral sex on men I don't know. My compulsion started when I was in my 20's, and I believe I understand why. I watched a lot of porn in xxx adult bookstores, and was constantly seeing closeups of girls performing oral sex on guys. The guys in this porn usually treated the girls roughly, using bad language, ordering them to do things, humiliating them, until the guys would cum in the girl's mouths or on their faces or bodies.
At first I identified with the guys when I watched these films, not because I was anything like them, but only because I was straight and it excited me to watch them get oral. But eventually, I started to identify with the girls and imagine myself in the female's place, instead of in the male's.
I also once heard a friend's girlfriend say that when she performed oral on a guy, she felt that SHE was in the position of power, not him. She said that she had his manhood between her teeth and while she would never hurt a guy, knowing she could made her feel power. Also, she said that she felt power knowing that performing oral on a guy and making him orgasm was giving him the greatest pleasure he could have.
So I know that my compulsion to perform oral on guys that I don't know, hearing them verbally humiliate me and order me what to do, having orgasms in my mouth and on my face and body, all comes from watching porn. That's why they need to be strangers too, because the guys in porn are strangers, and when the porn is over, I can go back to my real life. The first time I gave oral to a guy was in an adult bookstore booth, and I did it to satisfy my curiosity of what it would be like. But then I was hooked and kept doing it.
And I also agree that the thoughts of doing it, the anticipation before I do it and the fantasizing after I do it, are much better than the actual act. But I also experience huge amounts of shame at what I've done and that I've enjoyed any part of it.
It sounds like my compulsion is very similar to yours.