EX Flame WONT Leave Me Alone...

So, I have an ex flame who is currently bothering the HECK outta me. He's the kinda guy who uses girls for pleasure then treats them like crap afterwards. Well, he's been commenting on all my statuses and messaging me on facebook and skype. But, i'm afraid to completely block him because he has so much dirt on me. I trusted him at one point and all he did in return was hurt me. I go to school with him and I don't want him to try and ruin my reputation. I'm just a freshman and I have to be there for another three years... What shoudl I do?