Stomachache (sharp pain, stabbing feeling, not actually too painful) occurs every 25-30mins about 3cm straight on the right side of umbilicus. have been feeling like this for 2 days. currently on esonix to treat acid reflux. possible cause?

I doubt it's an esonix side effect. This symptom is nonspecific at this time. It may be caused by some degree of intestinal tract irritability, but observe for increased pain and especially localized tenderness, nausea or vomiting. These symptoms would warrant being seen by a physician or abdominal surgeon. Going to the ER would result in prompt attention & testing.