Acne on my ass!

ok look i got a serious problem with Acne on my ass about 2-3 years!!! doctors giving me many medicines that in the end Acne was still there stick on my ass!
the last doctor said that it was cystitis acne.I've read something in this forum that i didnt know,that liver cleance is the solution! is it? is this common problem?(on the ass)ive never heard any1 before that had Acne on the ass! bytheway i used to have on the face when i was young.

Pls i need serious answers, im suffering i cant even sit sometimes!
Thanks!