You're doing what I do, that is you're already worrying about tomorrow and tonight (I don't know where you are tho so maybe its closer than it is for me). Anyhow, first take the pressure off of yourself for tomorrow. Chances are you'll feel fine but that by worrying about it you can make yourself feel sick tomorrow. Just tell yourself if you can't go in, you can't go in.
OK, as for the here and now, it sounds like some gas, heartburn and/or acid reflux. None of which you are going to v for. Or maybe you just ate too fast and upset your stomach a little, again that won't make you sick.
I know its hard but try to distract yourself and think positively (beleive me, I know how hard that can be). Maybe sip some cool water, place a cool rag on theback of your neck, have an antiacid.
I hope this helps and that you're feeling better!
\"As soon as you trust yourself,you will know how to live.\"
Johann Wolfgang von Goethe
\"Do not anticipate trouble, or worry about what may never happen. Keep in the sunlight.\"
Benjamin Franklin