What Is The Itchy Rash On My Bottom Along With Pus And Blood?

I have red dry patches on my bottom that is very itchy, when I scratch a clear puss liquid comes out and if I scratch I also bleed and my skin also comes off into my nails, it has now reached my scalp. I can't control the itchy its driving me crazy, I try not to scratch the actual scab. I'm too embarrased to see my doctor, it looks gross. please help