Ex threatenings to sue / dealing with false accusations.?

My ex has an apartment in which I am currently living in. I am listed as an occupant on the lease. A few months ago there was a bad falling out. He accused me of cheating, slander, hacking his MySpace (never happened). He also says I am "squatting" by living here in this apartment. I am in a moving process, and he has not told me to leave nor has he given me any written notice to leave what-so-ever. He moved out, I stayed behind... and now I am hearing that he is going to try to sue me over this and emotional damages to him (I don't know what this means). The guy is a real psycho and I just want to know what my options are. Luckily, I'm moving into a new apartment tomorrow... but what rights does he have against me as an occupant in an apartment that he is renting but not living in? Had he asked me to leave or had he sent me a notice, I would have left much sooner...