Nobody here is qualified to advise you about your specific diet. If you are grossly overweight (and four stones certainly qualifies as that) you should never embark on a major dietary change without first consulting your doctor. Your heart, liver, and kidneys are all affected by rapid weight loss, and serious health problems can ensue.
You obviously need to lose the weight, but you should be doing it in a controlled and supervised way. See your doctor as soon as possible.