While we were in the states, I picked up some of those crest premium whitestrips as per everyone's suggestions on here. I read the pack, and saw that tooth sensitivity was a side effect, so I was expecting that I might get a little pain with cold/hot food as a result.Anyway, I used two one after another this morning (which is fine according to the pack) and now my teeth are aching non-stop. Is this normal? Surely by 'sensitive' they didn't mean that all of your teeth would ache constantly? Has this happened to anyone else