I have two light white spots on my front teeth barely noticeable. Not sure if I've always had them. I started using Crest white strips (the 14 day pack at a half hour each day). On the 5th day, I did things differently and I brushed my teeth first with Crest vivid whitening toothpaste before using the strips. After using my 5th strip, I'm noticing that one of the white spots seems more noticeable and whiter. I'm upset that it may remain this way. What can I do?? Did it strip my enamel too?