What Should I Do About Chronic Anal Pain For Over Three Years?

Hi. I am 32 years old, male, from Germany. Since 3 years now I m in severe pain constantly, radiating to the legs, lower back, etc. - I have a large sentinel tag and behind that at 6 o clock there is a very painful, swollen and sometimes inflammed area that s the source of my pain. I have tried many ointments, but they only help for a short time. After taking a photo, comparing it to pictures online and to the symptoms described, I am 100% sure I have a chronic anal fissure. But the Doctors in my country are unable to diagnose it. I ve had surgery before because they thought it was hemorrhoids, then they thought it was prolapse, nothing helped and I m only in more pain now. What can I do? Currently I am using Diltiazem ointment 2x daily, but it only helps if I don t sit down for more than a few minutes a day. I m a university student - I have to sit down for hours to hear lectures and write my papers...thanks.