I am stalked by my ex girlfriend for last 3 years....

I am stalked by my ex girlfriend for last 3 years. She harasses me every day by making 100 plus calls and getting inside my car from my office parking and keep me on hold as long as she wants. She abuses me verbally and physically and issue threat of murder and other consequences. What can i do. I dont want to file a police case as i think it can turn against me for having an affair with her. But that was 4 yeas back.