I know you are afraid. First of all can you tell me if your Dr. that you called was a medical physicial or a Pdoc?
I think if you decide to go to the hospital, you would just explain your symptoms and they would do a medical screening exam to determine what the problem may be,tests, lab work, EKG depending on your history and physical.
Most people that come to the ER do not know what is causing their problems and the physicians do not expect you too or you would not need them. Please don't let that stop you from going if your Doctor you spoke to did not want to guess what was wrong and suggested going to hospital if you continued to have problems.
could it be anxiety, yes but as your not sure and you have talk with a Doctor on the phone, I would do what your instinct here is telling you to. I think you want to be checked out now and if you do, go for it.
Hoping you will feel better soon.