Can I sue my ex for giving me herpes?

Yes, you would also be entitled to punitive damages as well. I would also report her to the Los Angeles County Health Department. This is not medical malpractice, this is battery which is a personal injury tort.

Absolutely. You should consult with an attorney as soon as possible.

Yes. However, proof in some case can be difficult and of course your personal life (and hers) become an open book. While punitive damages may be possible, proving and collecting are two different things. I would encourage any client to think twice before pursuing this sort of a case and discuss with them the strong likelihood of a defamation cross complaint. These cases can get ugly and expensive quick and I'm not sure there ever is a real "winner".

I would just add that many personal injury attorneys offer free 30-60 minute consultations. So, if you would still like to pursue this, you should set up one or more meetings and find an attorney with whom you are comfortable. If you pursue this, not only your girlfriend's life, but your own personal life and sexual history (as well as the personal lives of your other exes) will likely be central to the case. So, it will be critical for you to have someone who has experience in this area and someone you are comfortable with at your side in court, during depositions, etc.