My daughter is 15 and occasionally vomits for no reason and feels bloated. she had half of her thyroid taken out a year ago. what could be the cause?

Several things: This is a problem that necessitates a face-to-face meeting with your doctor. This will allow him/her to examine you, ask specific questions. And possibly order tests to find out what's wrong and what to do to help you.

Hard to say: Random vomiting is a non specific symptom.Its trigger possibilities range from digestive to hormonal to brain pressure and more.All can be sorted out with a thorough history and physical exam.Testing, guided by that information may also be needed.