Why cant I redeem my gift card? I bought it a couple of weeks ago and still says it is invalid code along with the on the bottom.

Was the iTunes card issued in the same country as your account is based (they are only valid in their country of issue) ? If it was and this page doesn't help then you will need to try contacting iTunes Support (you will probably need to give them images of the front and back of the card, and possibly its receipt) : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side ofde the page, then iTunes Cards And Codes