I'm the same, i'm 29 too and my same teeth are more faded than others. Its about the amount of sugar you eat i think, i'm mad on it, 2 sugars in tea and 3 in coffee, its no good for teeth lol
Use Pearl Drops its quite good, i use a whiteneing toothpaste and have been for years, it helps a little, i'm no Richard Hammond but in photos you do see the difference over the years.
But yeah cut down on sugary drinks, especially coke. The acid in coke softens your enamel then you simply brush it away from your teeth when brushing. They say that if you have a drink of coke wait at least 30 mins before brushing to allow the enamel to harden again.