Well, 5'9" is a bit better-frankly I am jealous you are so tall!

When I was your age I was 107 pounds and am 5'0"-I always have had a small pouch in the abdomen-even at that weight. The only thing I have seen work on that area is lower ab stuff. Tightening that area (although you cannot target lose weight!) will help shrink it and make it look better.