Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with 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:
How long has he had these signs?
Any changes in his breathing?
Are his gums pink or pale/white?
You noted he was put on Vitamin K, had he been exposed to rat bait?
Did his vet do any tests (ie check bloods, rule out tick borne disease, check his heart, etc)?
What did his vomit look like? Any black or bloody stools?