Teeth whitening

I'm worried because my teeth are much more yellow than before.
As I face increasing stress at work, I soothe my mind and relieve stress each time with sweet mixed coffee.
As a result, my teeth have become too discolored.
Dental teeth whitening also maintains its effect even when not drinking coffee, so I'm 고민되네요.

If anyone has had teeth whitening, I would like to hear your review.