First and foremost, anything you read online or in a book can at best be simple guidelines. It takes time to build your bull-crap meter, particularly for things you don't know a lot about. It helps to take a look at people who are successful at what you want to do with your life, and see what they did. Just be warned that if their site sounds like an infomercial, it's healthy to have a high level of skepticism.
Secondly, I think you may be suffering a bit from a lack of focused goals. That's normal, I started there as a full grown adult. So I would recommend the following:
- Take stock of where you are: What do you like? What don't you like? What are you willing to change? How much do you really eat? What do you really eat? Are you happy with your exercise?
- Set measurable and realistic goals: This can be anything from wanting to run a race to being strong enough for XYZ. Start with goals a little out in front and don't worry about life goals just yet.
- Stay away from extremes: If you want to loose weight, it might be tempting to cut your food in half. If you want to gain weight, it might be tempting to eat 6 cheeseburgers at a time. If you take steps from where you are (point 1) towards your goal (point 2), you'll have time to determine if those steps are in the right direction. Jumping off a cliff, so to speak, can cause lots of problems.
In all seriousness, if you really want to get rid of the extra weight, and not look skinny there are things you'll need to change. 15 minutes of cardio and pushups help a little bit. But if all you ever do is 15 minutes of cardio and the same number of pushups, your body will stop changing and you'll be wondering why. Same thing with only tanning for 15 minutes a day. You'll reach a point after a couple weeks where you don't get any darker.
This basic principle applies to whether you pursue racing (running, cycling, swimming), team sports, extreme sports, or strength sports (Olympic lifting, Power Lifting, Bodybuilding). Remember the last point? Each step you take will increase the amount of work you can do, and how efficiently you can train toward each of these goals. I recommend giving each one that interests you a shot. Give it a good 6 months each to see what you like the best. 6 months is long enough to get you past the complete novice stage and start building momentum towards a goal.
If you keep eating the same amount of food, but are much more active, the fat will come off (not necessarily the pounds). What's more than likely is that your appetite will increase, and you'll have to find out how much more of what foods you can eat and still maintain your short term goals.
I used to play soccer, then basketball. Later I got involved in martial arts, then power lifting. While I like each of those pursuits, power lifting is the one that I feel I want to keep pursuing. Your journey is likely going to be different than mine. The point is pick a direction, and stick with it long enough to start learning how to get better.