Lump Near Buttocks, Bleeding, Discomfort. Help

I have a large lump on the left side of my bum crack at the very top. It doesn t bleed often, but occasionally it does bleed a little bit and then stops. However it is uncomfortable when sitting on it - usually if I m slouching or something. I ve had it for many years as I am embarassed to see a doctor.. sometimes it bugs me and sometimes not. When it first started I thought it was just a bruised tailbone but then i discovered the large lump, kind of hard and like I said, occasionally bleeds