loose belly skin

I have a 10 yr old and 3 yr old. I am 5 ft and weigh 89lbs. I had both my girls naturally. Although i was lucky enough to bounce back without stretch marks i do have a little loose belly skin. It is impossible to get rid of. I do excersize every day and i feel that has helped but this last little bit of skin will not tone to my ab muscles! the skin is above my belly button.becuase i am petite it is noticeable. it almost seems like if I got my breasts lifted it would solve my problem. Id rather go about it naturally if anyone has better advice.