Well, the only advice I can give, is if you don't do sit ups, the floppiness will still hang around...
Its been 4 months since I had Aidyn, and I still have very much a jelly belly... it just doesnt poke out as much anymore.
I have been scared of doing sit ups because my mother attempted to do them 2 months after her first child, and she pulled a stomach muscle so badly, that she had to go to hospital!!