I think you are doing all you can. Yes, if all the tests are negative for heart disease, then depression can be the cause.
There is one more thing you can do for yourself. When a person is depressed and having physical pain, that physical pain is a substitute for mental anguish. That means you are sad or hurt that some part of your life is not working well. You should follow your pain, identify what is hurting you about your life, and be sure to talk about that with your psychiatrist. That is your best chance of being cured of all this suffering.
its caused by too much stress, i had it and it lasted about 5 days, if u get those pains just try to relax and remember, it isnt a heart attack and has nothing to do with the heart.