Whitening Teeth....?

Ok, im 15...and my teeth...well, there kinda yellow. yes, i brush my teeth, and use colgate toothpaste with whitening added to it...and listerien mouthwash. does the listerin whiteing stuff really work? i woul like to know some stuff that might really work befor i go and pay for it and it does nothing...wat about whitening strips too? do thos work as well??? Please, and thank you!! :D