Your tummy tuck was in October, 2010, and by your own admission, "went great." Although generalized edema after any kind of surgical procedure can be seen (it's called "third-spacing"), 20-25 lbs is an extreme amount, and it is now 7 months post-op. Surgery-related causes should now be resolved, and the fluid gone from this cause. Any lymphatic injury related to your tummy tuck would affect swelling only near your incision and in your abdominal tissues, not your entire body. And, they would be nearly completely healed and back to a new normal by 7 months post-op.
Cosmetic surgery may simply have been the "red herring" that was coincidental with development of your fluid retention, and your PS was wise to not prescribe any more "water pills." I would not have prescribed any, as edema related to surgery ALWAYS goes away on its own in a healthy individual.
This is why all of us are stressing the importance of a general medical evaluation to look into the causes of this degree of fluid retention--there are any number of causes, and some of them are serious. See a board-certified Internal Medicine consultant now! Good luck!