Worried about my weight :(?

14 years old, I'm 11 stone and 5 foot 4 inches and have a medium frame. I am overweight. I try and eat healthy for example this is one of my days - In the morning I'll have Special K flakes with orange juice, then in the afternoon, tin of Baxter's Soup with brownish bread, bottle of water, a piece of fruit, sometimes a chocolate (rarely) or a yogurt and for dinner I have what ever parents cook. I walk to and from school everyday which is 2.5 miles in total, I also do Horse riding on Tuesdays. I don't seem to be losing any weight in fact I am putting it on, how can I lose it and what exercise can I do after school? Can someone help me, I'm really depressed with my weight?