Hi welcome to Health care magic forum. Thanks for calling H.C.M.F. As you describe there is hot flushes, (hot flash across chest and upper back.)cold sweats , head ache an nausea. As you have hiatus hernia, and G.E.R.D. also when it is more it can elicit like this also, due to hyperacidity. Ofcourse it is also possible when there is fever associated with gastritisi it can be confirmed if you get fever in next few hours. Other possibility is jaundice confirmed by yellow urine and yellow eyes. But as it is mostly suggesting gastric symptoms i advise you to consult a gastro enterologist for diagnosis and treatment. You may have to go for gastroscopy besides other routine tests for confermation. Wishing for a quick recovery. Best regards.