Help?!!! ADVICE NEEDED ! :)?

My name is Paula. I'm 20 years old, im 5ft 3ft and 120 lbs. I have a slight problem. I have like a small belly that i want to get rid of. It makes me look like im somewat pregnant, And I dont want that. How would i be able to get rid of it. I was thinking i could to like sit ups to get rid of it. Please I need some advice guys! Anything is appericated :)