My 5 year old pomerian isnt eating and hasnt for 2 days ..

My pom has vomited 4 times in two days,he just lays around ,grimacing here and there. He looks like he is trying to go to the bathroom but cant-took him to the vet ..they said he could have eaten something outside,or it could be a gastr/stomach problem and we would need to be referred to another hospital..The vet did give him pills to stop the vomiting, and amoxicillin to try to help him, but he puked shortly after i gave him the meds-he did drink a little water, but otherwise just lays there-he is normally very energetic,its pretty sad to see him like this..any advice,do I need to take him to a different vet for tests or is there a sickness going around?? Please reply