You first need to determine the cause of the vomit. If there is an intestinal obstuction or the dog has a parasite problem, the pepto is not going to work.
If you have not yet seen the vet for a fecal exam, I suggest that you do so in order to rule out parasites as a cause.
For the vomiting, you should withhold food until the vomiting stops for at least 4 hours. Then you can give him a little water. If the holds this down, you can try feeding him a bland diet of only boiled chicken or boiled hamburger with white rice.
When he can keep this down, you can start to add his table food back in.
If you don't see any progress, he might have an intestinal obstruction that is causing the problem. If you suspect this, you should rush to your vet right away.
Let me know if you still have questions.
