I am so sorry you're going through this. I have been going through the same thing as you! Mine started in April. I went to the ER with intense chest pain, left arm and neck pain and shortness of breath. It felt like I was having painful spasms in my heart. They diagnosed me with costochondritis. My EKG and blood work were also normal except my heart rate. It was 160 there. My normal resting heart rate is about 115. They don't know why but don't seem too concerned. My chest and arm pain haven't went away and now I have pain between my shoulder blades. It is so scary to have to be worried about your heart non-stop. I have also visited my primary care doctor and he told me he's sure my heart is ok and doesn't know what my chest pain is from. So frustrating!!
Just wanted to let you know you're not alone. I hope the pain goes away for you!