Get checked for h-pylori you could have gotten contaminated by food or water. I felt the same a one time and thats what it was after test after test. It will get better but go see stomach doctor
Celiac disease, a reaction to gluten, is becoming more and more common. It now affects 1 in 130 people! Please get tested for gluten allergy. They should do about 3 blood tests. Even if you had upper endoscopy and they didn't see damage, you could still have it and it hasn't shown evidence of damage yet. If this is it and you go on a gluten-free diet, you will start feeling better soon. I had a friend whose only symptom was terrible heartburn. She had advanced Celiac disease. She was anemic and low in vitamin D and other vitamins and minerals. I think it took 3 months for her to get relief, but she did stop having heartburn. Every time she tries to eat gluten, the heartburn comes right back. And yes, having Celiac disease affects nutrition and you need enzymes sometimes, I think.