I haven't written porn in ages, but when I wrote it I rarely got turned on by it (often because it was comedy porn). I think I was like you; concentrating too much on words and descriptions, not to mention I couldn't write a fic in one go.

I've never gotten off on fanfic either, so to speak... I'm more likely to recall scenes from a story (or a few) while merrily on my way. The only time I've ever been turned on by my own fiction was around the time I decided I should probably find out about what this masturbation thing was but I suspect I was horny in general around that time anyway (late bloomer :')