There are lots of things it could be at this very early stage. You could have a little low blood volume from not drinking enough fluid, not enough salt in your drinks. Are you getting any broth? Water and tea will flush out the salts and the water will follow, causing you to feel dizzy. You're probably not on full diet yet, shouldn't be anyway, so try to get some salty fluids in.
There's lots of protein in gelatin. Milk products are pretty neutral in what they give you. Just don't try to survive on tea! It's dehydrating.
If it's really bad of course call your doc!!!!!
In addition to Zofran, your Nexium will quell nausea, and you should still be on that. If those don't work, ask for Donnatal which works differently, or maybe a scopalomine patch, like you should have had during surgery.