Is it normal to finger my own anus?

So about 3 times a day, when nobody is around, I like to roll my pants down and take my fist and insert it into my own anus. It hurts like a b**ch, but at the same time I scream with delight, sometimes waking the neighbors, and one time, my girlfriend heard me, came in and finished me off, which felt even better since it was my girlfriend doing it!

Is this normal?

P.S. Would the prostate be the male version of the "G-spot?"