GERD or a cardiac problem? Please help!?

Initially I went to the ER last month in June for severe chest pain and difficulty breathing. I was given an EKG and chest x-ray which were fine and they diagnosed me with GERD and anxiety. My family doesn't have heart disease but anxiety and GERD runs on my dad's side. My regular dr put me on protonix which seemed to work for a month until a few days ago where I had difficulty breathing and went to the ER again where I had another EKG and blood work which came out normal. My regular doctor did another EKG and blood work and that was normal too! The 2nd visit to the ER the dr told me to stop the protonix and to take pepcid 2 times a day instead. I'm honestly having a hard time believing this is just GERD even though it makes sense given my history. I am 22 yr old female vegetarian. I quit smoking and drinking coffee last month when all this started. I've also modified my diet and lost 10 lbs (wasn't heavy to begin with). I'm just really scared but I am diagnosed with anxiety which I am sure doesn't help my symptoms. I have an endoscopy Friday as well. Does anyone think this is possibly cardiac related or is it really GERD/anxiety? I just think it's odd because I don't cough up acid or anything but I do have a feeling of food in my throat. I also have on/off joint pain in the left arm. Do you think stopping protonix was the right move? Please help!