You obviously are trying to get yourself in shape. If you aren't spending hours in the gym doing intense weight training, you are probably not going to achieve your desired results, and may think about enhancing your program. However, keep in mind that you must not overtrain.
To avoid overtraining you need to make sure you give your body a break between workouts. The rest and break will help repair and beheld the muscle that is being broken down in overtraining.
Once you understand that when building muscle, muscle is breaking down, you will understand overtraining. You're not building the muscle in the gym, really. When you are inside the gym you are actually breaking down muscle and producing small injuries to that particular muscle that your body must then heal and repair. When these injuries heal and repair, they heal and repair stronger than they were previously. The process that actually builds muscle is that your body, while you rest, will repair the muscle tissue that is broken down during the workout.