Normekg,stress test,echo,holter.age28,nofamily history,nonsmoker.what would be another cause of mild chest pressure and numb chin feeling?still heart?

Not your heart: At 28 years old with no risk factors and all of those negative tests, it is safe to say that it is not your heart causing those symptoms, and you and your physician should look for other diagnoses. Gastroesophageal reflux would be a more likely cause. I am sure somewhere in all of this work up there was a chest x-ray performed which would have taken several other diagnoses off of the list.

Multiple causes: stress, tension, anxiety, chest wall inflammation, myalgia, neuritis...the list is quite long: consult your treating physician.

Esophageal: At your age with a normal stress test ( if it is nuclear MPI ) is very unlikely to be from the heart. I suggest looking for esophageal or gastric conditions ( GERD, esophageal dis motility )