I think it's great that you have conditioned yourself through dedicated training. You may have some loose skin, fat, muscles or all of the above. After pregnancy, weight loss, and age, the muscles of the abdomen can separate. This leads to loss of the defintion of the waist and abdominal rounding or "pooching". This may be in conjunction with loose skin and excess fat.
I encourage you to continue to exercise. Unfortunately sit-ups I have found that sit-ups usually do not flatten your abdomen because it does not bring your separated muscles together. More than likely your abdomen looks worse because the rest of your looks so much better. Once you have exhausted all exercise options, you may want to consider surgical correction.
From what you have described you may be a candidate for a mini tummy tuck, with or without liposculpture to the sides. This will flatten the lower abdominal pooch and add definition to your waist. The recovery is less than a full Tummy Tuck.
I reccomend that you seek a board-certified palstic surgeon for a full consultation and examination. Review with your surgeon what your goals are and the specific areas of your abdomen that you want to improve. I ask all my patients if they want to improve the appearance of their belly button and to point with one finger all of the areas they want to improve. I learn more about the most appropriate surgical options just by listening. Ask alot of questions. Review before and after pictures.
Hope this helps.
