Wow, It could be a number of things. I hope you can get him in to the Vets soon. Make sure he has plenty of water. Hope he's ok.
I agree. What kind of vet is this? Sorry this makes me mad, don`t want to upset you anymore than you already are.Blood and mucus in the stool can be alot of things. I can't believe your vet will not see your dog when it has blood in the stool and is vomitting.