| Okay, now we are talking. The fact that you are in high school leaves me to beleive that you may very well have access to a weight room as most high schools have one hidden away where no one can find it. Every school in my district has hidden away a weight room better than many gyms. Ask the PE teachers and if one says no you can't use it ask the other one.
Use the treadmill at your home for twenty minutes three times a week. If you feel too tired drink coffee or take an energy pill (no-doz or somthing like it) and go hard on it. avoid the temptatation to go on it every day or to go longer than is needed. Use that extra energy to just be more intense or to do strength training, or stretching or somthing.
Lift weights as many days as you can at school making sure that each bodypart trained gets at least 48 hours rest before it is worked again. The muscle groups are chest back shoulders biceps triceps quads and hamstrings. you can ask your gym teacher how to isolate them.
If in fact you really do not have access to a weight room you can get any number of exercise videos by fitness experts showing you good programs to build strength without weights. Tony Little dispite being very annoying and loving to touch his female assistants a little excessively really does have some good videos especially on how to train abs.
Now, seeing how you weigh as much as my left leg and have to squeeze to see any fat I would guess that you are not really overly fat but just lack muscle. Situps are in order to define that area. Cardio will help too because I do believe that any amount of fat is uncomfortable but muscle is the real cure here. Now that you are really training yourself to become better you need to becoem better at analizeing yourself. if you have one inch of fat on your body do not tell yourself that you have nine inches. they require very different programs and you will hinder results
Try to figure out how much protein and fat and carbs you are taking in. Keep carbs low (you decide what that means) keep your sugar lower (your call on how low) keep fat low and keep saturated fat lower (your call). Keep protein high, which in your case would be about a hundred grams of protein a day. I would say count calories but somehow I suspect that that is not the culprit
Do not rely on gym clas or vollyball to keep you in shape. it is tempting but they are not intense enough. fun yes but they won't help you. I am not trying to knock your sport (at least not at the momonet) but vollyball burns very few calories and builds very very little muscle  | 
