18' round pool leaning

We put up our pool about 5 years ago. When the pool filled with water one of the sides seems to be leaning a bit accounting for about a 3/4" difference in water level from one side to the other. Then to make up for it another side leans in a little bit. I have been convinced now for 5 years that our pool is going to collapse. I stress all winter with the cover on it and I'm out there once a week draining water off of it.

After the first season we took off some of the top rails and tried to bring in the round metal ring as much as we could on that side. I think what happened is that we made the bottom ring on the ground smaller than the ring on the top.

I was planning on tackling this problem when we have to replace the liner probably in a year or so.

Any suggestions on how to fix the problem. I've posted some pictures but it's tough to see in the pics the leaning.

Leaning in: http://i84.photobucket.com/albums/k1...12/pool001.jpg

Leaning out: http://i84.photobucket.com/albums/k1...12/pool003.jpg