PLEASE HELP. He will not leave me alone....?!?

I think you should talk to your boyfriend about it first. Then don't text but call the loser in front of your boyfriend and tell him to stop calling you because he's starting to scare you/make you uncomfortable and if he doesn't stop stalking you, you'll report him to the police (just to scare him off). Tell him you considered him as a friend but don't want to deal with him anymore because of the inappropriate things he's saying to you. Tell him you love your BF and don't want to be with anyone but him and wish him good luck in his life. If you're really worried and close to your parents then maybe you can have either of them contact him.