As a few previous posts mention, I too haven't had a real cock, but various stages of erection or flaccidness occur - depending on whats going on. It seems to feel better if I'm erect when I'm being pegged, whether with a strap-on dildo or a vibrating prostate massager by hand.
Just this past weekend, after intercourse when my wife came, I pulled out, layed on my back and enjoyed a little stroking while my wife cooled off a bit - my vibrating prostate stimulator was in.
I found myself with my legs fully open, knees up near my chest - full "fu@k me" position. My wife held my leg up and open for a bit so I could enjoy being fingered by that stimulator. Then, hearing me moan a little, she moved down and sat between my legs and started pegging me with my prostate stimulator - first slowly and controlled, then faster and harder. She was hitting my g-spot and I was loving it. After about 10-minutes of varying ecstacy, I shot my load all over my chin, chest, and stomach. I maintained an erection the whole time.