I'd be worried too and probably be looking for a second opinion. Vomiting can be caused by so many things. Is the dog at least drinking water?
I'd withhold food for at least 24 hrs but have water available (you need to worry about dehydration). When starting to feed, start small meals of chicken and rice and see how that goes.
I have had good luck with a sensitive stomach dog (as did my son with his dog) on Pro Plan Salmon for sensitive stomachs.
Hope this helps but you really may need to get that second opinion!!
Go to another vet immediately. Continuous vomiting can be very serious or fatal. You need to find out what is the cause immediately and to stop it. Your current vet is obviously not helping so take the vomit and your dog to another vet immediately. Put the vomit in a ziplock bag so they can analyze it. It is very helpful to the vet.
First of all, sorry about your Dobi problems. My wife and I have (3) females, and they really do seem to have sensitive stomachs.
Hill's makes a stomach-sensitive food called 'Hills i/d', but it's prescription only and usually only available FROM the vet (or you can order online as long as you have an Rx for it). It's worked EXTREMELY well for our crew, but Neutro works well also.
May I ask exactly WHAT he's vomiting? Meaning, what color is it? (IE: watery, yellow & foamy, food particles, brown bile-colored, etc). Also, have you ubrutly changed his food recently?
In the past, we've used a combination of the below (see links), and it usually clears up their tummy, but we tend to lean towards Hills (which, incidentally, is way more expensive than the Neutro):
Neutro-Natural (dry):
http://www.petco.com/product/109122/Nutro-Natural-Choice-Herring-Meal-Rice-and-Potato-Formula-Adult-Dog-Food.aspx?CoreCat=DogFlink_SensitiveStomach
Neutro-Natural (wet):
http://www.petco.com/product/12055/Nutro-Natural-Choice-Chicken-Meal-Rice-and-Oatmeal-Formula-Canned-Food-for-Sensitive-Stomachs.aspx?CoreCat=DogFlink_SensitiveStomach
There are so many things that can cause vomiting. I was wondering what kind of test were done and does he have diarrhea? If all the blood work and other test are fine it is possible that he may have swallowed a foreign object. Sometimes a barium swallow is helpful. They assist the dog in swallowing a white, chalky, liquid and then take several x-rays over a period of time. Sometimes a regular x-ray may not show the object. I would go back to your Vet. and have them do some more test. There has to be a reason for the vomiting. The Vet. can give you a medication to help with the vomiting if it's not a foreign object. I do know that on rare occasions a dog will eat too fast and the food comes back up. Make sure he gets plenty of fluids to avoid dehydration. You may have to give small quantities at a time. Maybe you can find a flavor of Pedialyte that he'll drink or let him lick ice. Usually it's best to withhold food while their still vomiting to let the digestive system rest but only for a few days. I would recommend using a Science Diet dog food you get from your Vets. It's called ID and works very well. Feed in small quantities to see if he can hold it down. If he's not better shortly I would take him back before the weekend or you may have to pay an emergency fee and the longer you wait the weaker he'll become. Hope everything turns out okay.