>>33407260 (OP)Yeah, OP. That's one of the easiest things to fix.
Use these.
Specifically these ones. You might think "sensitive" means they're weaker, but the fact that they have a lower strength of bleach means you can use them much more than the standard ones, to actually get your teeth properly bright white. Yes, the one with the light helps (UV light speeds up oxidizing reactions, which is why it's bad for your skin but good for bleaching your teeth). The good thing is that the light is reusable for multiple packs, so just buy one kit with the light and a couple more without it.
After you get them pretty satisfyingly white with these, then you go to the dentist if you want, and tell them to spot-brighten any areas that weren't covered by the strips.
Dentists can offer you tray whitening, but trays are more likely to long-term damage the nerves and prevent you from eating ice cream/etc.