Was the drive shaft good when you installed it? You should always move it around on both sides and check for too much play or over-tightness.
I'm kind of confused on where you have play however. Is it in between the male-female splines where you connect it to the half shaft? Or is that joint tight, but with the 3 bearings on the inner half giving you lots of play?
If you want to test Type-R-Dunk's theory of having dropped a bearing, you could probably feel around the inner boot from the outside to see if you there's a bearing floating around in there. It's pretty big you couldn't miss it if it's floating around in the boot.
It that comes up with nothing, make sure your half shaft isn't bad. If you move it around and it's very loose, replace it. There can be a little play however.
If that's fine, and you haven't dropped a bearing on the inner half, and there's still play (or tightness) on either side of your drive shaft, you should replace it again.