My 14 month old's stomach is bigger than normal, she aint eating much, one night she woke up vomiting. she is currently on anti biotics medication called clarihexal for hand, foot and mouth. what can be the cause for the huge stomach?

Bloating: The stomach will swell with excess air when the kid swallows it during or between feeds & it does not move down the GI tract as it would normally. The medication or the illness may be the cause. I see no reason for a kid to be on antibiotics for HFM, a common viral illness. Clarihexal is a antihistamine, not an antibiotic. I see no reason it would be helpful.