I haven't changed my eating habits and if anything i should av lost weight cos i've been walking more but instead have put on a stone in last 4 weeks?

Look at the calories: One should choose an exercise he or she really enjoys. Any form of exercise burns calories, so if one does not eat or drink more calories than she is using during her exercise, then her body will burn up fat as fuel. However, if a person drinks a large orange juice (about 300 calories) while exercising, and exercises away only 200 calories, she will still get heavier even though she is exercising.