Penal Code section 273.5 is what's known as a "wobbler" in California - it can be charged as either a felony or a misdemeanor. The police will always arrest you for and book you under the felony, but it's up to the DA to decide what charges (if any) and what level is appropriate.
The first question for you is: Is the DA going to file? I don't know - they will review the entire police report and make their decision from there. If they do file, is it going to be a felony? Doubtful from what you described here.
Even as a misdemeanor, a conviction for this charge can have lasting consequences far beyond going to jail and court. It sounds like you have a good defense and should NOT accept any deal without first discussing the facts with a good criminal defense attorney in your area. Do not speak to anyone about this - no facebook, myspace, texts, emails - nothing. Consult with an attorney in your area as soon as possible to figure out where to go from here.
I do domestic violence cases throughout the SF Bay Area. I have 35 years' criminal litigation experience. I agree with the prior advice not to plead. If you have not yet made your first court appearance, you should hurry and consult an attorney, because there is something he can do to help convince the prosecutor NOT to file any charges against you. The case CAN have long lasting consequences against you, even just the arrest can.
For further info on DV cases you can read these articles on my web site:
My contact data is also on there, and you can call me for a free telephone consultation about your particular situation and I can tell you if I think I can help you.
Note: The general answer below does not constitute legal advice nor does it create any attorney-client relationship between us. For further information, feel free to contact my office for an initial consultation at www.PrometheusLaw.Blogspot.com or by calling 510-910-3198. I have offices in Santa Cruz, Campbell, Redwood City, Oakland, and San Francisco, CA, and I practice Family, Business, Property, and Criminal Defense Law, providing top-tier legal representation at affordable rates for working class clients. While I cannot give legal advice outside of an actual attorney-client relationship, which would entail forming a formal written signed contract, thus allowing me to fully review and analyze the specific facts in your case and conduct the necessary research into the law on point, generally speaking I would answer your question as follows, though this is not legal advice and you should definitely seek an attorney's guidance re: this question of yours:
You may have a good case for self-defense, but an attorney should look carefully at this. Hopefully, you can acquire good character references, witness statements, and you don't have any priors. This may all help. I handle such matters at affordable rates.