I can also relate to some of your concerns
1. Unless I can fuck really fast, I don't feel much pleasure. and if I do fuck fast and hard I get out of breath very quickly
2. I also get grossed out by poop and even just the smell of it can put me off to a point that I don't feel like fucking anymore.
that is why I'm also a bottom, but unfortunately I can only seem to hook up with guys that are either only top or only bottom. which makes it hard to switch when I don't feel like topping.