My boyfriend BOP status became ' not in bop custody' and his release date is 'UNKNOWN'. I cannot get touch with him. Does it mean he has been released?

This means that he is probably in a facility that is not a BOP-run facility (but he is in custody somewhere). Do you know if he had to make a court court appearance? This would make sense, that if the Release Date is Unknown it might mean he is awaiting sentencing, either someone on his case has not settled and therefore his sentence has not been handed down. He definitely has NOT been released.  Once he is designated to a BOP facility, the locator will identify where he is and his actual release date.