How do I stop a yahoo user from harrassing me online?

I need help. For over 1 year, a yahoo customer has been signing me up for various things. It is someone I stopped seeing. I have been able to trace 16 emails back to his email address. I am beginning to get very scared. He has used my name and email address to sign me up for various advertisements. They all have to do w some health issues I have. When I go to unsubscribe, I find that his email address comes up. He has signed me up for spine surgery, wheel chairs, singles sites etc. I have them all in a folder. He sent emails to the Senators of my state, and I received the answers. He is using not only my name, but my email address over and over again. My Father passed away recently, and when I had to send an email to the funeral home his home town comes up when I try to type in mine, and his email address. He is signing me up for things w his address of Batman1for02@yahoo.com I can't get any help because he hasn't threatened me yet. I am afraid of him. I know that changing my address is an option, but I know that you can always be found online. If you could help me, I'd appreciate it. I really need some help. Sincerely, Lisa Helms darkshades4evr@yahoo.com