I loaded a gift card into my iTunes when I already had a positive balance and only the new card is showing up. Not the total of the cards I have entered? Is this normal or should I see the entire amount of the two cards?

You shoudl see the total. Have you tried logging out and back into your account on your computer's iTunes and seeing if the correct amount then shows ? And you didn't have any auto-renewing subscriptions or pre-orders that were due, you've checked the purchase history on your account ? If logging out/in doesn't change the amount and there aren't any purchases then you could try contacting iTunes Support and see if they can help : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption