Constant chest burning mid chest somewhere between breastbone and neck. all cardiac workups good. doesn't feel like heartburn. is gerd possible?

Yes: Burning chest pain with neg heart studies and no cardiovascular risk factor is gerd until proven otherwise. Change your diet and avoid food that trigger the chest pain like coffee, sodas, fatty fry food, spicy/hot food, acid fruits, broccoli, garlic, onions etc. Loose weight if overweight, avoid tight clothes, don't eat 2h before going to bed, eat 6 smaller meals a day, exercise.