key

So, I bought the game through Steam and decided to give the multiplayer try. I noticed it needed an ea account in order to connect, so I created a new one, filled my information in there, put my email, password, and cd key... the usual. As I click on the "confirm" button the game would give me the following error, that the cd key I inserted is invalid. I kept retrying but I'd be given that same error, over and over.
Later on I'd try a different method on ea's redeem a code section on the website, as suggest by the support. But now, when I try to make a log in in bad company 2 multiplayer, after had already redeemed the code on ea's website it recognizes my key is already in use, and it won't allow me to proceed through the  log in authentication. Please, send help!