Up until this last year (I'm in my early 30s), for all my life, as long as I could remember, even back to childhood, the only way I could masturbate to orgasm was by imagining myself as a man raping a woman. (I am female.) The man was never anyone I knew, and neither was the woman (she was often young, btw). No other type of fantasy would get me to orgasm.

Fantasies are just fantasies. If they don't bother you, then you're fine.

But for what it's worth, I'll share my experience: my fantasies bothered me, though after a while, I denied to myself that they did. Really, for me, they were an indicator of a whole lot of other underlying, repressed issues. I got into therapy over a year ago for reasons unrelated to this, but this is one of the many things I've talked about and dealt with in therapy. My fantasies have been slowly evolving to include other types of fantasies, ones which are not so distressing to me, and I'm usually actually in my own fantasies now (imagine that!). This involved a whole lot of exploration of childhood and adolescent issues, and it hasn't been easy to talk about these things and deal with them. But for me, it has made a big difference.