I get pain in my heart, left arm and left jaw. 3 years fully investigated by cardiologists. but it's definitely not in my mind. what else could cause?

Pains...: Assuring you definitely had the heart investigated by cardiologists, it could be nerve related-meaning the nerve that innervates those areas is irritated or inflamed in some way, causing the pains. Anxiety is always a possible cause too. See and work with your Primary Care provider to get to the possible answer and treatment. Best wishes.

Many things: Esophageal reflux, a pinched nerve in the neck, muscular strain and lung lesions can all cause chest pain. The important thing to remember is that these conditions are not life-threatening. However if the pain continues to bother you , I would persue a definite diagnosis and treatment plan.