What Causes Hard Lump At The Rectal Opening?

I noticed a small bump on the inside of my anus almost a year ago. It is on the top and just inside the anus. It feels as if it is movable but it also seems hard. It has caused me on and off discomfort. At times it will itch uncontrollably and I will bleed heavily when I go to the bathroom. At other times, I completely forget that it is there. At times when its really irritated, it will burn if urine comes in contact with it. Please help.