My head hurts I'm vomitting and my legs hurt

Could be a number of reasons. How long have you been feeling ill? Any fever? Any recent physical activity? Around anyone recently ill? Any discoloration to your legs? Have you tried pain reliever?
Try sips of water fairly frequently if you are able to keep it down to prevent becoming dehydrated.

You'll have to decide how badly you feel and whether you need to call your doctor or go in and get checked, or if it is more like the flu and you will have to rest and wait it out.