The problem is that the email you used for ME2 has to be the same as the one you use now for Origin.
If it's not, when you will launch the game with Origin, it will log you into EA server with the origin's email, and so it won't detect your Cerberus code ..
What you can do is effectively contact the EA support (live chat in preference) and explain to them that you didn't use anymore this email and ask to have another code.
But try to give them your old cerberus code and ME2 key, and maybe your old email if you can remember it ...