Photography help....?

Im 15 years old and I am an aspiring photographer. Right now I have a canon rebel xsi camera that I bought with my own money, and an 18-200 mm zoom lens. I know it's a great camera and I've had it for around a year, but I feel bored with the pictures I'm taking and I don't feel like I'm getting any better at taking pictures. I don't really have much money to spend on new lenses or cameras, but I don't know how else I can improve my photography. Please help!