This new security feature has been in effect for quite some time now. It happens whenever you try to login from a different geographical location. Usually the locations have to be outside the range of a typical commute.
How many miles/kilometers separate the three locations you mentioned (home, boyfriend's, and work)?
If you continue to access your account from all three locations on a regular basis, the system should learn that connections from those locations aren't out of the ordinary. You should
contact Blizzard if the account locking persists.