I'm curious about teeth whitening.

My teeth weren't originally white, but lately I've been paying more attention to themㅠㅠ My skin is quite fair, so they seem to look more yellow somehow. I don't even drink coffee... I'm curious if teeth whitening really works and how long the effects last!!! Also, since my teeth are somewhat weak, I experience slight sensitivity, so I wonder if teeth whitening is possible... Please share experiences from those who have actually tried it :)