Find yourself somewhere secret and safe, a women's shelter if necessary, and call the police to see what they can do.
You've probably done irreparable harm to your credibiity, because the question "were you lying then or are you lying now?" will be difficult for you to answer, but you've got to get away from this man, because as I'm sure you know he'll keep hurting and threatening you, no mater how many times he apologizes and says it'll never happen again.
I'm only licensed in CA. This answer doesn't make me your lawyer, and neither do follow-up comments and/or emails and/or phone calls --- we need an actual agreement confirmed in writing before any attorney-client relationship is formed. Thiss answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue.
If by domestic violence case you are talking about a CLETS DV temporary restraining order filed in the family law courts, then you should be able to file a new request for temporary restraining order. There is no need to "reopen" your previous case. If he is committing other acts of domestic violence, such as telling you he will kill you if you lie in court, then you have new grounds to ask for a new order.
If by "domestic violence case" you are talking about a criminal case that involved the District Attorney's Office and law enforcement such as police, then I would suggest that you contact the District Attorney's office in your county or the City Attorney's office if you are in Los Angeles and let them know that you want them to continue with the case against your boyfriend. If the prosecutors dismissed the case against your boyfriend before going to trial because you previously refused to testify, then the prosecutor has up to one year to refile charges again.
In any event, it sounds like your boyfriend has committed several violations of law, including dissuading a witness from testifying, and making criminal threats in violation of Penal Code 422. You should try to get these threats on tape and present them to your local police department. They will have him arrested immediately and will likely seek emergency restraining orders against him to protect you.