What Is The Treatment For The Stretched Belly, Skin And Muscles?

hi I am 20 and had my son two years ago as he will be 2 in june! he was a big baby considering I am only 5 ft 2.and he weighed 7.5 stones! since having him he stretched my belly,and the skin/muscles have never got back together again! Ive tried exercising but no difference has been seen! I haven't spoken to anyone about this ,but is there anything that can be done under NHS?? as I am not working and cannot afford to pay for the surgery needed.