How to check your accounts:
You can see if your EA Account is linked correctly to your EA ID, Xbox Gamertag, or PlayStation Network ID that you play Mass Effect 3 with on your N7 HQ account page.
If you see your Origin ID, Xbox Gamertag, or PlayStation Network ID listed on that page you will be able to view your multiplayer data on the N7 HQ.
How to tell what account my Xbox 360/PlayStation 3 is using?
On console specifically, EA games that connect to EA servers will automatically detect and use an existing link between your console account and an EA Account from a previous game. This means that while you are automatically logged into an EA Account playing a game, it might not be connected to the EA Account you are using here. It may instead be connecting to an EA Account created previously, perhaps when you first played another EA game on that console with a different Xbox Gamertag or PlayStation Network ID.
If you are not sure which EA Account is attached to your Xbox Gamertag or PlayStation Network ID the EA Help Center has some useful entries specifically around detecting this. Search for "Account" related entries, such as this one: "Linking Your Gamertag, PSN ID, PSVita ID, or EA Classic Screen Name."
A BioWare Social Network (BSN) account is an EA Account.
The account you use to log into the BioWare Social Network is an EA Account. If you use the same account on the BSN as you use to play Mass Effect 3 you can also log in with that account on this site.