What Causes Burning And Itching Sensation On Rectal Area?

I have had burning and itching in my rectal area for years. Here lately I was getting a little blood on the toilet paper after a bowel movement but hardly noticeable. But now I'm getting enough blood about nickle size that will soak through the toilet paper and I'm becoming concerned. I also feel a sharp pain like I might have a blister just inside the anus.