Mejo,
I don't often go on this forum (usually on the F&F of Alcoholics), but I have worked in the DV field for many years. I'm sorry the police did not charge him, but I do have a suggestion (apart from the great advice you've already gotten).
Please go to the ER and have your injuries (the neck bruising and any internal injuries to your throat) evaluated. You may not THINK they are terribly serious, but they could be. There have been instances of death from strangulation that happened days after the incident.
Also, once you have done that, you can contact the DA's office and ask that they take a look at your case. The police don't have the final say on whether to prosecute, the DA does.
Regardless of whether you want to pursue charges at this point or not, however, do see a doctor. Have the injury documented, and treated if necessary. I hope he will never have the opportunity to hurt you again, but if he does, that documentation can be important to a later case.
I'm so sorry this happened to you, and regardless of what the police do, please pursue that order of protection, and connect with a DV advocate who can help you with safety planning.
If there is anything you want to ask me, feel free to pm me.