Nicole, I'm replying just so you don't think you're being ignored. Unfortunately, I don't have the answer on how to fix your problem, which is why I didn't reply to your other post. We used to have a gent that posted here that installed pools, but he hasn't posted in a while, I think. I do hope someone else can answer your question. If not, then your next best bet would be to find a reputable pool builder in your area and have them look at it.
Nicole 12, when did you noticed your pool to be leaning or rather tilting? And since then, did it deteriorate further? Your 3/4" is the level differences between the 2 longer ends or the shorter 2 sides. How much are the vertical sides (wall) leaning as compared to other sides? What are your pool's dimensions?
Post your figures then the gurus will take it from there.
It could just be that the ground has sunk or heaved under a bottom rail. Do you have frost in your area or a high water table? Sometimes its just a matter of shaving down the substrate in one area if the rest of it is level. Frankly I'm not convinced that it looks horribly off - I have seen worse but level is always best if possible.