Any way to whiten naturally yellow tinged teeth?

My teeth aren't horribly yellow, as I don't smoke or drink coffee, but they do have a yellow tinge to them. My hygiene is fine and I have tried all types of whitening products, but nothing seems to help. When I was a young child, my mom asked the dentist about it and she said that some people just don't have the genetics to have pearly white teeth. I have become incredibly self conscious about it and am looking for advice or suggestions. I just bought the crest white strips advanced seal and have tried 2 treatments, once yesterday and once today for 30 minutes at a time. I really don't see a difference, whereas people said they saw a difference after just one treatment. What do you think?