I struggled with a bad slice as well, but I got rid of it from LOTS or video and practice. Once your muscle memory is used to your swing, its HARD to change it overnight. But, It sounds like your dropping your body on your follow through. Causing you to "Duff" or hit behind the ball and your swing could be a "Out to In" swing path, could be numerous things. I fixed my slice but making a stronger grip and slowing down my take away and back swing a ton. I also payed attention to how I was addressing the ball, I was WAY off when I was slicing, body was all jacked up and didn't even know it. Make sure your body is lined up where you want to hit the ball, take your time and swing easy, it will come. Get your swing on video to see where your flaw is.