Depression causes all sorts of problems, both physical and mental. For me, I was "convinced" that I had some serious digestive problems. It turns out that depression was making my digestion a really difficult task to complete. When I had a full physical exam and an ultrasound, it turned out to be my mind making my body ill.

If you're on medication, some meds can cause nausea like that. Perhaps you can keep a journal of what is going on before, during and after the chest pain episodes. If you notice a pattern, then maybe you'll figure something out.

Best wishes to you in your struggle.