I have dealt with chest pains and wondered if it was heart or anxiety. For me @libby93 I use the method of sliding my finger down my chest while applying some pressure. If the muscles hurt then I know the pain is coming from anxiety.
That said it is possible to miss a heart problem. My mother had tests done and nothing showed. Then her heart went into afib and the doctor ordered a echocardiogram with dye that showed heart damage from scarring due to childhood disease.
So be aware that anxiety can cause chest pain, but it can also have other causes. So please keep seeing a doctor and get a second opinion if you feel it is necessary. Please keep us informed on your progress towards solving this