Still got jaw pain three years after onset of tmj despite every treatment. is this likley to go on its own?

Every treatment?: Not knowing your specific situation, whom you've seen and what you consider "every treatment" it's impossible to give you an accurate answer. It sounds like unless there is some change in treatment or doctor, it might well continue to go on. Have you seen someone in your area who has extensive training and experience in this area? Consider going for a consult at a dental school.

TMJ: It would be helpful to know what treatments you have had. 90+% of TMJ can be treated successfully with a hard acrylic nightguard splint and patient compliance. Seek a dentist who has had extra training in TMJ treatment. Surgery is the last and worst option. Sometimes orthodontics to correct malocclusions is required as well as splint therapy. Let us know how it turns out.

Rx causes not sympt: You need to find someone that can help you find out why your joints and muscles are not working properly. These problems do not appear without causes and you need to find the causes to begin to find the proper treatment. These situations also do not "fix" themselves. Check with your dentist for someone who can help you find answers that will help.