It could be either or. It's hard to say.
Eating gluten again after three months could very well be causing your stomach/intestinal distress, particularly if you were gluten-sensitive/intolerant to begin with.
If even sipping coconut water is making you grumbly, I wouldn't eat or sip anything right now. Wait it out. Take a nap. Rest. Then re-hydrate with coconut water, chamomile/peppermint/ginger tea.