Ex keeps harassing me

My ex the father of my 2 kids will not leave me alone! He has no time for our kids, but will text me hateful and hurtful things daily. It is starting to really affect me emotionally. I’ve tried blocking him but he tells everyone I stop contact with the kids, but when he’s unblocked he doesn’t mention them. He continuously calls me degrading names, starts false rumours about me, texts me abusive msgs about guys he assumes I’m seeing, threatens guys I talk to, he actually bashed one of them, he tries to befriend guys I’ve been with and will tell everyone they said I’m bad In bed, childish shit like that. He went as far as to record his friend make a rap swearing about me to some music just to send it to me. I feel like giving up and I don’t know how to handle all this harassment. I now feel as though I should involve authorities and put a restraining order or put him up for harassment as he doesn’t know when to stop and is only getting worst! I don’t think a charge will stop him completely but at least he will have to deal with the consequences instead of getting away with it.