OK so I have this ex and I broke up with him and before we dated we were good friends and then after he wanted nothing to do with me and I kept telling him that if he ever changed his mind then I would be here and all that.
but then all he did was text me call me or leave me messages saying mean things to me, calling me a c*** and a slut and and the thing is I'm not any of those and it just pissed me off. So I told him that I wanted him out of my life and to act like he never meant me if he is going to act the way that he was
but... he won't leave me alone and he still randomly calls and harasses me
my mom wants to take leagl action against him for harassment
is this the right thing to do?

Most likely I don't know how often randomly is, every day, once a week, twice last year?

But of course the time you should have was when he was doing it all the time, But obviously he has some real issues and that may be the only way to get him to go away.

I think that your mom is right in wanting to take legal action. Did he treat you this way when you two were together? This is harassment, you told him to leave you alone, and he hasn't.

I agree, this is harassment and should be dealt with as such. If not nipped in the bud, it could lead to more dangerous activity.

GET YOUR NUMBER CHANGED!!