Firstly, I am not in the medical profession so you can take this as my own experience only. I suffer from Costochondritis
. That is a condition that inflames the soft tissue
that surrounds the breast bone and caused symptoms very similar to the ones you are describing. it took my doctor several months to come up with this diagnosis ans I was then told, after an ECG and a treadmill, that Very few chest pains are caused by the Heart but all should be professionally diagnosed.
Keep pestering your doctor for as long as you are suffering is my advice. Get second or even third opinions. This is not only affecting you but also your friends and loved ones, they do not like to see you suffering, so keep at it.