What can I do to reverse enamel erosion of my teeth :'( ?

i'm 15 but my dentist says i have the teeth of a 60 yr old.. i had braces for 5 years.. i got them when i was 10.. i was just a kid so i wasn't worried about taking care of my teeth and it shows. they're all yellow and yucky. what can i do now apart from veneers, etc? we're not that rich