slow weight loss

Hi, I have been on 1000-1200 cals a day and working out an hour a day five days a week but have only lost 1 pound in three weeks, I used to be able to lose half a stone in two weeks,I really don't know where I am going wrong has anybody any tips i.e filling food for low cals, at the moment I have porridge with a banana for breakfast, salad for lunch with a yogurt and either a weight watchers meal or chicken and veg for dinner and I'm always so hungry so I really can not lower my food intake, thanks