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:
Did the gum color change start with these signs?
Any retching, gagging, lip licking or vomiting?
Can he keep even small sips of water down?
If you press on his belly, does he have any discomfort, tenderness, or tensing?
Could he have eaten something he should not have (ie bones, toys, plants, chemicals, etc)?
Has he had any diarrhea? What color?