Being harassed...

I'm hoping someone here has experience with the law regarding harassment. My boyfriend's heroin addict ex girlfriend will not leave us alone. She and her friends have messaged me multiple times over the past 3 months. Calling me a whore, saying they hoped I miscarried, and today she posted a picture of me saying something along the lines of "how do you go from this, to this?" I am stressed out and depressed. To the point where I don't want to wake up tomorrow. I feel like a bad mother because I am so depressed and cry all the time. My relationship is being ruined. She has multiple social media accounts that she uses to stalk and harass me. Is there anything I can do? Will law enforcement help at all? Can I file for harassment? Or would I need to sue with a private lawyer? I am in so much emotional distress. So is my boyfriend. And we have a 2 week old. I can't take any more of this and I know it won't stop on its own....