Just a fetish? Not having doubts but a little confused.

Just a simple question...now that I've committing to starting HRT soon, hopefully before the end of the year, I start imagining myself as a woman in various scenarios, like this morning when waiting for a bus, I imagined a version of my current reality where I was further along in my transition.

The thing I have noticed, is when I start doing this, it also turns me on and I start getting hard. Just wondering how...normal that is. I've been into TG captions and erotica since my late teens, and it makes me wonder if I am confusing a fetish for a desire to transition...

I'm going to try HRT regardless to see how I feel, but would like some feedback on this point with people sharing their experiences.