I’m so very, very sorry that life has been so difficult for you for so long. Although I can’t make a diagnosis on the basis of a letter, what you report is consistent with a major recurrent depression. It sounds like you’ve done all the non-invasive, non-medical things one can do. Give yourself credit for how hard you’ve worked at this.
If you haven’t already, please see a medical doctor and get a thorough physical exam. There are a number of medical conditions that can cause or contribute to symptoms like yours. We want to be sure that there isn’t an undiagnosed medical condition. If everything looks fine medically, the next step is to see a psychiatrist. (Perhaps you’ve done this already but you didn’t mention it.) Psychotropic medication may help jumpstart you enough out of the depression that you’ll be better able to make good use of your therapy.
If medication fails, there is ECT (electroconvulsive therapy), once called electroshock treatment. Although a treatment of last resort, it is often effective in treating a prolonged depression like yours. During ECT, light seizures are induced while you are under anesthesia. It isn’t clear just why it works but it is regarded as both safe and effective. Like medication, there is a chance of side effects. You and your doctor would discuss whether the chance of those side effects is outweighed by how miserable you’ve been feeling.
I encourage you to educate yourself about available medications and ECT and to discuss these options with your psychiatrist. There are still some treatment options you haven’t explored. I hope one of them gives you the relief you deserve.
I wish you well.