Hello, I'm Dr. Deb and will do my best to help you today.
I'm sorry for this concern about Billy. There could be any number of reasons why he's vomiting ranging from dietary indiscretion to viral or bacterial infections to Inflammatory Bowel Disease to a foreign body to systemic disease...just to name a few examples.
But, regardless, there may be a few things you can do at home for him as long as he's not extremely lethargic and his gums appear to be pale pink (not white or blue) and he doesn't have significant abdominal pain.
1. Over the counter Pepcid AC (Famotidine) can be given which help reduce his nausea. The dose would be 10 mg twice a day for a dog this size.
2. Withhold food for at least 8 more hours or so and just give everything a chance to settle down.
3. If the nausea appears to be well controlled, then offer only a small amount of boiled, skinless, boneless chicken breast and 20-minute boiled white rice but only a small amount at one time.
4. Limit water intake as well since to do otherwise may stimulate more vomiting. Offering Pedialyte is a good option since it can replace electrolytes lost in the vomit.
If he continues to vomit and/or develops any of the other signs I mentioned, then a vet visit may be prudent. I always worry when these older dogs become ill in this way since they can deteriorate rather quickly (they don't have the reserves of their younger counterparts).
I hope this helps and that you see improvement soon. Deb