This is potentially tl;dr, but I am in dire need of advice.
You broke up with your SO about a month ago and have no intentions of getting back with him/her. Since then, s/he has oscillated between trying to get back with you and sending you texts to the extent of "fuck you; you'll be sorry." One night you fall asleep well before midnight, and apparently your ex really wants to speak to you that night and texts/calls you dozens of times (but to no avail, as you are sleeping). At about 3am you wake up to pounding on your bedroom door. You initially ignore it, but after 10-15 minutes, you go outside and discover your ex is waiting there for you. S/he flips out on you, and you eventually convince him/her to go home. After coming back and banging on your door again, s/he eventually goes home.
S/he has also threatens to withhold your mail (you two used to live together, and you still need to change your address), stop payment on a check s/he wrote you, and message your friends and family members (in hopes of turning them against you?). S/he coerces you into hanging out with him/her (by threatening to do some of the aforementioned) and the whole time tries to force you to kiss and touch him/her. You realize you can't cope with this anymore and decide to sever all ties, but you can't help but fear for your safety and well-being, as s/he is so erratic and unstable.
What do you do? Do you go to the police, wait it out and see what (if anything) happens, or otherwise? Thank you in advance for any input.