Like Briar, I hope you no longer need this advice, but years ago, our ped gave us a "stomach virus formula." You give 1 teaspoon of water and wait 20 minutes, then another teaspoon of water, wait 20 minutes. Repeat a third time. If during that first hour, no vomiting occurs, you can give 1 teaspoon diluted ginger ale (this advice was geared for older children--you could probably adjust this and maybe express a bit of breastmilk and give 1 teaspon of that.) Anway, if the vomiting has stopped, you then can move to a clear liquid diet and the following day, the BRAT diet. If, at any time, the vomiting begins again, you go back to the beginning with 1 t of water.
One of my dds is particularly miserable when she has a stomach virus--she'll vomit often for a good 12-18 hours--and there have been a few times when we thought she'd have to go to the hospital, but she always turned out fine. (Whenever she's sick like this, it's always either a weekend, or we're out of town.
: ) The very worst time, we were staying with my BIL who was a pediatrician. He told us it was an up-in-the-air call about whether to take her to the ER or not, so we decided not and she gradually improved.