My puppy is really sick after immunizations.?

I took my 3 month old Schnoodle to the vet 2 days ago on the 4th. He received his immunizations for Parvo virus, Distemper, para influenza and Hepatitis(CAV-1). These were all shots he had at 8 weeks old as well with no reaction(according to the breeder). He had his shot at about 1 in the afternoon. He was fine until the morning. He became very tired. Wouldn't eat or drink and would just lay around. I called the vet and was told to give him some benadryl and some syrup to help raise his blood sugar from not eating. I gave him the treat and he perked up shortly after. I did not give him the benadryl since he seemed ok. He seemed fine and 100% by the next a.m.(which would be today) We started seeing him get lazy again and he hadn't eaten his food at all. Then he started to dry heave, and eventually vomiting. This has gone on all day and is not right. I called several vets at home(of course it's the weekend) and they all said I was doing the right things (pedialite, maple syrup(for sugar) and letting him rest. I did go ahead and give him the benadryl too. I tried getting him to eat cottage cheese, cheerios, but nothing. I am going to stick with just fluids now. He has finally drank some water and not thrown up. Its been about 2 hrs. He even went potty(pee) I will also mention that his stool earlier today had a yellowish, snot looking streak in it. They have other wise always been perfectly formed and regular. I am so scared that something is really wrong. I love this little guy(Biscuit) and so does my 6 yr old and husband. I just wonder if its the immunizations or flu or what. Had anyone had a similar situation or know what it could be and what I should do. Please any info would help!!!!