Welcome to HealthcareMagic. For the darkened skin, apply creams containing Kojic acid
or Aelaic acid are useful. Other treatment options which you can get done are chemical and glycolic acid
can also be done, but this might require several sessions. Skin resurfacing using lasers is also an option.
For the big tummy, eat more of salads and fresh fruits and vegetables. Eat less of fried stuff and start doing mild exercises concentrating on abdominal crunches after getting the nod from your gynecologist. You can go for walks also.
Hope it helps. Regards.