If you are seriously motivated to loose weight, don't give up & don't keep saying "I'll do it tomorrow". It takes roughly 30 days to make something a habit. If you keep saying you will start tomorrow, you never will.
First of all, find something to help motivate you. When I gained 20 pounds I started watching exersize, diet, and health videos on youtube. That helped me start working out and eating healthy. I also looked at celebrities that I want to have my body look like ( or as close as possible lol). Do you have a friend or relative to work out with? I would always go with my sister (she was overweight & trying to loose weight too) so we motivated each other. When there were days where we just didn't feel like it we'd use 'tough love' and make the other go. Even if you just do 15 minutes of cardio! It's better than zero. Always remember that. Getting a gym membership would be your best bet. If not, then you can always work out at home, there are plenty videos on youtube. Since you have a treadmill, you should start walking at a fast pace for as long as you can. Shoot for 10-15 minutes and eventually build your way up. Then you'll start jogging/running. Stretching/yoga also helps as well because it creates lean muscle & keeps you from hurting yourself. Don't do weight training too often because your muscles need to rest. Maybe do weight training 3 days out of the week. One day focusing on upper body, one day on lower, and one day on EVERYTHING. You can do cardio everyday if you'd like. The best would be to do it 5 days a week, even if it's just for 15 minutes. Try and do it as long as you can though :P
As for diet, this is the MAIN key to loosing weight. Cut out all fast food, non diet sodas, really sugary foods (like cake, cookies), and if drink coffee use organic sweetener & organic or 2% milk. If you eat/drink all those you'll loose 5 pounds from that alone. I recommend going on an organic diet. Organic is usually less fattening, has less sugar, no chemicals, etc etc. It's just all around better for you. Be sure to eat a lot of vegetables, fruits, lean meats or fish. Try to stay away from foods with a lot of sugar, sodium and carbs, but do not starve yourself from them or else you might end up binging on them. A good thing to do is to pick a day where it's your "treat day". Lets say you choose Saturday. So Sunday-Friday, you do good on your diet and exercise routine. When Saturday comes, you can eat some of the more fattening foods without going crazy. Something not TOO crazy, like a nice dinner and some low calorie dessert. That will keep you from binging and it will help motivate you to eat healthier. Try and restrict your calories to 1300-1900 a day. Look at the nutrition facts too, sometimes foods can be lower in calories but have a LOT of sugar or fat. You should also bring your lunch to school. Cafeteria food is VERY unhealthy.
A good idea is to switch to 100% whole grain/wheat bread. If you eat cheese or drink milk, try and get 2%. Grilled chicken, tilapia, salmon, turkey, and (only on occasion) ham are very good meats for you. Good snacks are things like fruits, organic and/or low calories snack bars. Luna bars are great meal replacements. only like 220 calories, organic, DELICIOUS (iced oatmeal raisin is the best), and VERY high in vitamins.
You need to do this for YOU, nobody else. If you keep this weight up or it gets worse, you can have health issues in the future. Don't listen to what anybody tells you. If someone is being rude to you, use it as a motivator. Prove it to them AND yourself that you can loose weight. Also if you mess up and binge or get off your work out routine, DO NOT GIVE UP! Keep going! Chances are that will happen, it happens to practically everybody. Especially with the holidays coming up. WHEN you get the weight off, which you will, you're going to have to keep it up. It's a lifestyle change. You can't go back to how you are eating now exercising. You can be a little bit more lenient though. One more thing, don't focus so much on how much you weigh. Muscle weighs more than fat in case you didn't know already. Just as long as you're loosing inches, your weight does not matter :)
I'm sorry this was SO long, I didn't realize it lol. I hope you had a long enough attention span to read it lol. I wish you the best of luck & don't give up <3 You'll be there in no time. GOOD LUCK!
just experience & loosing weight myself. I'm not an expert or anything, although I'd love to be a personal trainer :)