After "just a few hours" you need to wait and let your body do its thing. You, however, need to stop eating and drinking - even water. If you are still vomiting after 12 hours and not eating and drinking, then you can call the doctor. If you are feeling thirsty, suck on a small ice cube for a few minutes and wait 30 minutes before doing it again.
Go to the E.R. Throwing up that much is potentially very serious. You can damage or even rupture your esophagus, or at the very least, you'll start dehydrating quickly. I won't begin to guess what's wrong, you need to get to the hospital where they'll give you anti-nausea medication, iv fluids, and figure out why you're vomiting so much. Seriously, go to the E.R.... ASAP!