HELP!

So i haven't used my Apple I.D in a very long time. I have been all about Android until recently when i purchased my Mac. Well i went to go buy music with a gift card that the Apple store had given me for buying my Mac…seems simple enough. I redeemed it into my account. Then when i go to make a purchase, it says i need to update. After updating my username, password,and email and everything is all set… my gift cards have been erased!!!!!!! Someone help me!!!