Does anyone know why this person is going so far as to try to ruin my life?

I don't really understand this person but it seems like he/she really enjoys toying with my emotions or manipulating everyoen around me. He wants me to get me committed to a mental hospital and spreads slander about me to other people so that they don't talk to me. None of the people I talk to tell me who is doing this though they drop hints that there is someone out there who is doing it. This person bugged my phone lines, stalked me to all of my contacts, accused me of being a threat to national security, tries to know as much about me as possible like my weaknesses and my strengths, or past fallouts with friends, and he wants to thrust it in my face or get others to say this to me in order to ostracize me. I feel helpless, yet no one seems to see it as a big deal, the police thinks that I am crazy, and this person tries to find ways to show me that he is watchign me all the time and doing it by staslking me online and backstabbing me. I don't know what is his problem, but he has been doing it for a year. Everyone thinks that it's my fault although I have done nothing. What has been going on?