I've never had a protein shake, as on Atkins I find I get enough protein from what I eat, so don't know why it should make you sick. Did you use anything else with the powder that could have caused a reaction? Maybe your body is reacting to an additive?

I have used protein powder to "fortify" soups for my husband when he was ill and I worried about his protein intake and also added it to baking recipes.
So if shakes do not agree with you but you are not getting enough protein with your food choices maybe you can find a way to add the powder to your foods instead?