How can I effectively whiten my teeth?

I quit smoking some time ago, and I do drink coffee, but not excessively... My teeth are yellow. Is food the problem... I don't really have any particular concerns, though. ㅠㅠ

Actually, I didn't pay much attention to the color of my teeth and didn't realize it, but my wife asked why my teeth are so yellow, and when I looked, I definitely noticed that they are a bit more yellow compared to others.

Maybe because I paid more attention, but since then, I feel like it looks a bit more yellow every time I see it...

I've been using whitening toothpaste for a little over a month, but there's no noticeable change. I guess I should go to the dentist.ㅠ

I'm just continuously searching for good products before going to the hospital.