I need help

I have had this problem aswell
You must cut off the other hand, there is no alternative.

Or just accept that you have some sort of anal fetish.

There's nothing wrong with you man. The prostate is an erogenous zone for a lot of people - man and female. It's no different from a guy who likes having his balls played with, or a girl who likes having her tits played with. Some people enjoy it, some don't. You're one of the the ones that does.

My advice? Find a girl that can work with that. They're everywhere, believe me.

It's not a big deal to have a kink but if you want to stop it duct tape your hand to your desk or whatever or you could jerk off with both hands