After some research on the net, I found that if you don’t drink coffee much or chew tobacco, there’s a good chance that your teeth aren’t stained at all. In this case, if you use tooth whitening toothpaste, you probably won’t notice a difference in how white your teeth are.
Also, in the last couple years, it seems that all toothpastes are “teeth whitening”. Chances are, you’ve already been brushing with “tooth whitening” toothpaste. Continuing to brush with “tooth whitening” toothpaste isn’t going to make your teeth any whiter since you’ve already removed the stains with previous tubes of “teeth whitening” toothpaste.
Try visiting a dentist to have your teeth truly whitened and assessed.