What you should do is not post anymore details about this online, and call an attorney to speak with them privately and confidentially. You yourself are potentially at risk for filing a false report, and your partner is at risk of a felony. Both of you need to hire counsel immediately to protect yourselves. Only an attorney can assess your specific situation, and determine how best to proceed in either clearing this all up, or protecting you should the case move forward. Either way, call an attorney to protect your rights.
I agree with Mr. Turnoy's assessment; you are in a difficult spot. As a defense attorney I want to stress a few additional points: The prosecuting attorney is not your attorney. You do not have attorney-client confidentiality privilege with them and they cannot give you legal advice. The prosecutor can use your statements against you similar to the police. The same goes for any Victim's Advocate or victim's rights person, those folks are usually DA employees.
All of the above also applies to your domestic partner's defense attorney; they will happily paint you as a liar, false reporter, etc. if it helps get the client acquitted. His defense attorney would be happy if you come out of this with a conviction for false report or perjury because it will make it harder for you to ever prove charges against your partner in the future.
So for all of the above reasons, you should consult with an attorney. The Oregon State Bar can make a referral for someone qualified in your area.
It is important that you tell the truth, no matter what it is. You can tell the prosecutor what really happened, but ultimately it is up to him or her to decide whether to proceed. You might also want to consult an attorney of your own who can advise you on how to proceed.