I think it stems from people like the OP and myself having such a poor self-image that we believe if we were ever to engage in any sexual activity with anyone, that person would be damaged somehow.
I certainly shy away from people to avoid infecting them with my damagedness, but it's not sexual. (I do worry about whether I'm "good enough" in bed, but that's another issue.)
I don't fantasize about any girls I know, but that's what porn is for. It all seems kind of silly now that I've thought it over and typed it out.
It doesn't sound silly, but I do worry, and please don't take this as criticism, but I worry about
why you don't fantasize about girls you know. I doubt you're the only one, but this does seem to feed into the division of real girls untouchable up on pedestals, and sex off in another zone entirely.
People fret about the accessibility of porn giving adolescents unrealistic notions of what real live sex actually is, although I'm not sure if reading the racy bits in
Clan of the Cave Bear at age ten gave me a more accurate idea. But it does seem a shame that most boys (and girls) these days will have seen a
lot of porn before they get to turn theory into practice, and I wonder if it doesn't underscore the notion that sex is "bad".
(Sorry, I'm not doing a very good job of articulating this.)