Try blocking it - like we do with show quilts. Rewet well in washer, and then lay it out on the floor. Using a square in each corner, put a lot of pins in holding each corner flat and square. Pull and push to straighten out and increase size as much as possible - holding with pins into carpet. Let it dry. If necessary, touch up with an iron.
This blocking will make the quilt look so much better, and bring back a portion of it's size. It really does help.
I'm so sorry this happened to you. It must have been the batting. I can feel your disappointment from here :(
I sure hope the blocking helps...a lot!
Debbie in Austin