Would he be considered a stalker?

[Diana]

I came to realize that my ex-boyfriend is obsessed with the idea that if he can't have no one will. We broke up almost a year ago. And six months ago I started dating someone who I now love very much.

After breaking up with my ex, he left to live with his mom, but came back to break in while I had company and demanding that person to leave. I moved out since, ten miles away. While I was walking my dog, I ran into my ex boyfriend at the parking lot. He followed me there. He sends e-mails to my current boyfriend telling him that I am going to leave him for someone else. Sent him a screenshot of one of the conversations I had with one of my facebook friends. I don't know how he has access to my account.

I am still good friends with my ex's sister, and through her phone. got a hold of my new phone number (now disconnected).

His actions are creating problems in my relationship. How can I stop him?