Hi Michael, we are here for you. Please do not give up. If you are not getting help from your doctors, try new doctors (if you can). Try to get a better diagnosis.
Please consider anti depressants. Several people here have taken them to tide themselves over the worst times. It is nothing to be ashamed of. If you are having destructive, obsessive thoughts, medication can help you deal with them and allow you to focus on healing.
Can you tell us more about your situation? Do you have a good diet? Are your stools soft and formed or are they hard and dry? Or do you get diarrhoea? You say you do sitz baths. What else do you do? eg, exercise, relaxation, painkillers like ibuprofen or lidocaine? Are you using creams or ointments such as nifedipine, diltiazem or nitroglycerine? Do you feel your doctors are taking good care of you?
Do you have family to turn to? The terrible irony of this disease is that it's so hard to talk to people about it. You tend to suffer in silence. With other injuries or diseases you get sympathy and support, but with anal fissures you tend to isolate yourself. Even one friend to talk to can make a big difference. If you haven't anyone like that, please keep posting here. We are here for you and we want to help.