I just received a subpoena. I was a victim of domestic violence. I told his parole officer that I did not wish to testify. What can I do?

You can make your wishes known the prosecutor.  The problem is you are just a witness in the case.  The Commonwealth has control of the prosecution and they can compel you to testify if needed.  Especially in Domestic Violence cases the victim does not want to testify by the Commonwealth has the duty to protect everyone and your abuser may represent a danger to the community, in which case your wishes are less important than the greater good.  Speak openly and honestly with the prosecution and consider retaining your own counsel if things start to get messy.