So many of you have written but never posted. Let's get those stories done and out. 
I'm a f'ing slow writer. So much so that my 'mind' is usually one or two stories ahead of my Word documents...
It totally is a bitch 
I do get off from them from time to time, but not while writing them... More like 'inventing' them...
I totally feel you on that.
I have about half a dozen unfinished stories, four that I'm currently working on, and more then a dozen other ideas kicking around inside my head.
Doesn't seem to be letting up either.
In fact I just got a new idea this morning that is just too delicious not to write.
My feeling is that if you aren't getting at least a little aroused while writing sex scenes then it's pretty crummy erotica.
When I get hot while writing I kind of lean into it.
I try to craft my words in a way that turns me on even more because that's where I want to take my readers.
The closest thing I can compare it to is edging.
If I don't stain my boxers with precum I feel like I'm not doing my job correctly.
This seems to work for me, but mine isn't the only way to go, and I would never tell another writer that their method is somehow wrong.
If it works for you then go that way, but I know what works for me.