hitting behind the ball

I had a previous thread on here about how my softball swing was negativly effecting my golf swing. I tried some of the things that people replied and it really helped.....i am slicing the ball a lot less, and hitting the ball farther.
The only problem is, my swing is inconsistant. Last year, I topped the ball a lot. This year, it seems I have the tendancy to hit behind the ball, like way behind the ball so i hit through a section of grass before i even touch the ball, and the ball hardly moves. Can someone please explain to me why I might be doing this and what i can do to fix this problem and hit the ball more consistantly?
Thank you in advance for your replies.

Could be a slide - try my Table Drill (Tips from T.C., C.P.G.A.).

You might be dipping or bobbing up and down, causing your swing to be ok, but now you're closer to the ground than you were at address.

I could be way off track here but check your backswing. Are you swinging back free and easy with no tension, tension going back can put your body in strange and tense positions. As a little test just casually place the club at the top of your backswing and stop. Feel comfortable and relaxed? now continue with the shot, do this 10 times and see if you are striking the ball better (you wont get distance because you've relaxed the bodies coil) we are just checking your positions.
A tight backswing can make you sway(side to side) and pull your uper body down towards the ground then when you commence your downswing you have to change many things in a split second to get back into the correct position.
Focus on only one thing( for me its the brand name on the ball) and relax. Did you know breating in and out during a golf swing changes your body position. Relax half a breath in hold it and start your swing.

Hope this is of some help