iTunes doesn't recognize my ID, can't update apps

I'm trying to do an app update, but can't because the store won't take my ID. I had modified it on my computer so that it had my new e-mail address,

but I can't modify it on my iPod because it keeps saying my debit card code is invalid (I don't even remember which number is the code!).

Even when I try to sign in using my modified account, it won't recognize my password. I have reset my password at least three times!

Please help!