I went through this a few years ago- it’s horrible. I would have episodes of nausea and heartburn that seemed to last forever. I’d have to force myself to sleep sitting up bc the reflux was so bad some nights. I went to an allergist. I went to a GI specialist. I even had an EGD done which only showed minor damage to my esophagus from heartburn. I was prescribed omeprazole and ranitidine and would still have the episodes despite taking it for months. Along the way, a few people told me it might be due to stress and unfortunately I took offense to their comments. At the time, I truly felt that any stress I had was completely under control (I was wrong). With a lot of time and some self care, the nausea and heartburn went completely away. I don’t take medication and during periods of high stress when it creeps back, I’m able to control it. Stress can do some weird stuff.