So I bought crest white strips, and I've used these before. It was years ago for prom, but I loved them and had no problems. I started them just last night, and I woke up this morning with terrible pain and sensitivity!! It's miserable!! I spent like 40 bucks on these! And I have 20 days worth of strips. Should I throw them out and get married with not-so-white teeth!? I don't know what the hell I did wrong. I made sure to read the instructions more than once! Anyone have this problem before?