I was in a lot of pain and took 3 percocets--now I feel so dizzy and faint-spacey.How do I feel better? I feel really scared and anxious.How long until it wears off?

It's probably going to take a couple of hours to wear off. You may start vomiting also. At this point there is nothing you really can do but to wait it out and use this as a lesson. ALWAYS follow medication directions.

How much do you weigh?

Try to eat, it will help you lose that floaty yet queasy feeling, and also help you sleep more normally and help calm the buzzy ringing sensation you might get when you try to sleep on all that oxy. And drink some gatorade, pain meds can dry your system out, and also make you really constipated, might want to take a laxative also.
But you should be fine unless your allergic to opiates, I took about 20 at once after I was in a bad accident, thank god my plans fell through, although I was sick as a dog and my ears were ringing for a good three days...
Hopefully these suggestions will help you out a bit more than having to hear a life lesson in the middle of puking from a bad buzz.

try to eat, it will help you lose that floaty yet queasy feeling, and also help you sleep more normally and help calm the buzzy ringing sensation you might get when you try to sleep on all that oxy. And drink some gatorade, pain meds can dry your system out, and also make you really constipated, might want to take a laxative also.
But you should be fine unless your allergic to opiates, I took about 20 at once after I was in a bad accident, thank god my plans fell through, although I was sick as a dog and my ears were ringing for a good three days...
Hopefully these suggestions will help you out a bit more than having to hear a life lesson in the middle of puking from a bad buzz.

Umm since this post was on August 22, I'm sure the OP is feeling better right now.