Why can't I lose weight?

I am sure this question comes up all the time! But I am getting desperate. I am getting Married in August next year and will have to order my dress in the new year, I am very over weight and wanted to lose alot for the wedding. I weight about 14 stone (196lbs). The last few weeks I have been really trying with not much results! For example on an average day I will have bran flakes cereal for breakfast, a tin of soup for lunch which is 180 calories, no bread or anything then later maybe an apple or banana and then for dinner I have been having a weight watchers microwave meal with fresh veg or salad. I know the microwave meal is not very healthy but this is a temporary thing until Xmas. I am a member of a gym and the last few week have been going alot! and I do push my self because I do cles. Last week I went Body Combat on Monday, Swimming on Tuesday, Body Pump on Thursday and Spinning on Saturday and was shocked when I stood on the scales yesterday and stayed the same! I honestly thought I was in for a big lose! My friend lost 5lbs this week and she is slim anyway!