CRADLING the baby she never knew was growing inside her, 13-year-old Charlotte Maddox still cannot believe she is a mum. For months after sleeping with a boy of 15 she dismissed fleeting pains as a tummy bug and thought she was "a bit podgy" because of overeating. Her parents noticed nothing unusual. Then two weeks ago, racked in pain, Charlotte went into labour with baby Sophie - and at last the astonishing truth dawned. She said yesterday: "I was screaming in pain and shouted 'I've got to push something, it's coming!' "That was the first time I realised I was...