It's tough to answer not knowing any specifics about your situation, but most nausea is not form a GI source. It could be secondary to a medication, anxiety, endocrine issues like low AM cortisol, electrolyte imbalance, headache and other neurological conditions. The list is long. For people ages 15-25, anxiety is the #1 cause in my experience. Next is what we call functional nausea, basically a neurological cause for nausea. See a GI doctor if the nausea gets worse or affects your ability to accomplish your daily activities.

Tough to answer with the limited information you’ve provided, but it may be acid reflux. Please consult your doctor.