You may have silent reflux. Or you are getting all this down to stress? Do you suffer from stress badly? This can cause chest tightness. It is also a sympton for reflux though. However, stressing badly can bring this on as well.
I know how you feel as I'm going through the same at the moment. I've not done anything apart from stress the past few years to bring my silent acid reflux on. I've never had a diet of spicy fooRAB, high alcohol or caffiene intake. So the only thing that is causing my problem is stress and anxiety. That's what I'm thinking now anyway from reading on here and through google.
Try and remain positive. I know its difficult, especially with chest tightness, as when that happens - I'm sure like many people, you think its an heart attack.
Take care