Why arent i losing weight? :(?

im trying to lose weight but it just seems like im putting more on than im losing. last time i weight myself i put on 2 pounds in 3 weeks. i have already given up crisps and i barely ever eat chocolate. i dont drink fizzy drinks. i have started jogging twice a week as well as riding 3 days a week and doing pe either one or two days a week. i also try to do some yoga or dance at home. today i have eaten two oranges, four crackers, a cereal bar, a bowl of stew and half a marmite sandwich. so why am i not losing weight.