Hi, We often need help from others. Know you are young and have plenty of time to improve. I would suggest praying if that's something you believe in.... if not maybe you should reconsider turning to God. Talking to a therapist can also be helpful. Call your local mental health dept for an appointment. Its often not too costly.
You have been depressed for years. Their are many reasons for depression. They really don't know for sure why people get depressed. The chemicals in the brain are not rights. I found out I had high mercury levels after many years of depression. This was caused by my amalgam (so-called silver ) fillings. It took over a year after removing the silver-mercury filling and a heavy metals detox to start feeling better.
Do you have a lot of amalgam filling. The ones that look like silver? This can be a cause of metal health issues. Did your mental health go downward after getting these fillings? This is just one idea that can cause depression, but more common than not.
Best wishes, JC