Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one 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 apologise that my colleagues could not aid you sooner. If you would still like assistance, can you tell me:
Can you tell me if he can keep water down?
What did his vomit look like?
Are his gums pink or white/pale?
Since you noted rapid breathing, are you seeing more then 30 breaths per minute?
If you press on his belly, does he have any tensing, soreness, discomfort, or tenderness?
Could he have eaten anything he should not have (ie toys, bones, socks, rocks, plants, people medication, toxins, etc)?