Sometimes dogs just get intestinal upsets which can be fixed easily, and can be attempted to clear up at home as long as the dog is acting fairly normal otherwise, non-painful, not pale, not dizzy, no longer vomiting, and eventually will eat. If it doesn't clear up at home, then a vet appointment is necessary, as antibiotics or deworming or just something to settle the GI tract may be needed. Also, although watery stool and straining is common with diarrhea, sometimes a partial foreign body ingestion can cause this and it's very important to keep a good eye on him the next couple of days to make sure there is continued improvement.
Do continue to offer water if he'll drink. (If not, he can always have some unflavored pedialyte). Try offering a bland diet like boiled chicken or boiled hamburger meat with white rice (1:1 ratio). No treats, and don't let him eat grass either. Continue this diet for a couple of days as the stool firms up. Once firmed up, gradually go back to the regular diet over the course of a few meals. Usually they will attempt this type of diet after some time if not forced.
If needed to get him more settled and to start eating, you could also give Immodium (loperamide), which dosing information found here:
Make sure it has been 12 hours since you gave that pepto, and don't continue pepto, as it contains aspirin properties and can lead to stomach ulcers and thus feeling sicker with continued vomiting. Try this, and if not clearing up in a couple of days, you'll want to make a vet appointment then, or if looking worse by tomorrow, seek a vet sooner.
Best of luck, and let me know if I can help further.