Hi, Have Loss Of Appetite, Chills, I.e. Feeling Cold, Then

Hi, have loss of appetite, chills, i.e. feeling cold, then warm, lots of burping after trying to eat small amounts of food, nausea. Not sure what it is. No pain. The doctor recommended ultrasound to tull out gallstones. Then a blood test for pylori bacTERIA. no endoscopy yet. This has been going on for a month, 1 week feeling better, the next nit. Thank you! BIANCA