Have you tried a bland diet of chicken and rice? You might try that for a few days and cut it down to smaller portions every few hours instead of one or two large meals.
You might ask the Vet about giving Pepcid to see if that helps.
Were x-rays done at all? Were fecal samples tested?
Have you changed foods?
Did your vet give him an injection? Cerenia seemed to help with my dog's nausea. Also, try giving him a little water, wait for him to swallow and keep it down, then a little more water. It may be that he's drinking too fast or swallowing too much air.
You might want to ask for a barium study. It could show if there is a blockage or something getting in the way of his food passing through. Are you treating him with Pepcid? Is he losing weight? There is a prescription appetite stimulant for dogs but you need to find out what's causing the vomiting first. A 2nd opinion from another vet can't hurt. I wish you good luck!