I'm 16 years old and currently on my period i've noticed at night i get a burning feeling in my stomach and nausea what could that be?

? Reflux: Possible reflux of stomach contents / secretions into the esophagus especially when lying down, common, multiple causes for such problem: caffeinated beverages, fatty meals, being overweight, and others, try to avoid the triggering factors, elevate the head of the bed, drink water, and use OTC antacids / PPI (as prilosec) but read the labels carefully, if still suffering, see your doctor, goodluck