Oh man, here's one subject I'm almost ashamed to have expertise about.
Does it hurt when you go to the bathroom?
If so, it's very possible that you have an anal fissure that can't heal itself due to, er, lots of hard stool keeping it open. Most of these can be treated by increasing your daily fiber intake and drinking lots of fluids, or by using stool softeners, to give it time to heal. Apparently there are medicated creams that can be prescribed. However, it's highly unusual for a fissure to last for one and a half years -- they're supposed to heal in the short term just like any other cut, if not prevented by the factors I mentioned above.
I don't really see how it could be caused by wiping too hard -- unless you're using sand paper or something, which I assume you're not. It's more likely to be caused by... an overtight anal sphincter. In this case, make absolutely sure that you're never sent to prison.
There's actually a surgery for chronic anal fissures, but only if you want some dudes cutting your bum hole. Correction, -inside- your bum hole.