help! is 112 pounds, and being 5'1 and a half fat?

Well, I can't really say. But you could check your BMI (Body Mass Index) to see where you fall.

Here's a link to one: link

I doubt you are "fat" by the description you've given. That seems kind of harsh on yourself! Just exercise for a half hour or so most days of the week. Cut down on sugary, high-fat foods and stick to more natural things, like grains, fruits, and veggies. I've had a lot of dietary success being a vegetarian.

just chew gum all day,but at night eat the K cereal

Cut out certain foods like breads, soda, sugar and potatoes. Stick to an all natural diet and exercise any time you can like during the weekends.