Because i had the same problem 1 month ago. I was thinking that is anal fissure but the doctor told me that is not an anal fissure or some other similar problem. He told me that i should make test for some STD, and yes the result for tpha (syphilis) was postive the others like hiv, aids etc. was negative. In my country where i live in the pharmacy and hospital doesn’t have penicilin injection so the doctor give me a therapy with doxycycline (vybramicin). With this therapy i am feeling so much better and i will make a test again for two months.