Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.
Again I do apologize that my colleagues could not aid you sooner, but can you tell me:
Could he have eaten something he should not have (ie medications, plants, chemicals, bones, etc)?
Can he eat or drink since the vomit? Can he keep it down?
Are his gums pink or pale/white? Moist or sticky?
If you press on his belly, does he have any discomfort, tenderness, or tensing?
Has he had any diarrhea?
Any changes (redness, sores, odor, etc) in the ears?