What sprocket, (tooth count) are you currently using? The higher the tooth count the lower the gear ratio. A 48T sprocket will pull hills better than a 44T. A 56 will almost let you climb trees but your top speed will suffer. Think of a car with a manual transmission. A small sprocket will be like leaving the car in a high gear all the time. A larger sprocket will be like leaving the car in a low gear.
Tom