Leaving my 6 month lease early?

I decided to leave my lease 3 months early but, I paid in full the 6 months of rent when I moved in, plus the security deposit. So now my landlord is being a jerk and he wont give me back my other 3 months rent. My question is is now that I am leaving early I know he can keep my deposit but I want my 3 other months that I paid ahead back. Is that possible? Please HELP!!!