FBAR and Schedule B

Hi,

I have a foreign account with over $10k and I reported the $100 interest on it as if it was a 1099-INT. But I never completed a Schedule B or FBAR, until today until I read about it.

Do I have to amend my previous years return just to check "yes" and file a Schedule B? I already reported the foreign interest in those years. If so, how many years do I have to amend?

Thanks