Hello & welcome, I am Dr. B,a licensed veterinarian and I would like to help you with your wee one today.
How old is your dog?
What is he bringing up in his vomit?
Can he keep any water down?
Are his gums nice and pink (not white/pale)? Moist or sticky?
If you press on his belly, does he have any tensing, tenderness, discomfort, or pain?
Could he have eaten anything he should not have (ie bones, stones, socks, toys, plants, chemicals, human meds, etc)?