I know your boat exactly, actually i read it and thought i was reading my own post. I can’t really help you on the bulking up except to say try a full body program but I can help you with the fat loss.
You’ve probably heard by now to eat six meals per day because it boosts your metabolism. I agree strongly with that statement. Being a teenager you should probably be eating about 2000 cals to mantain a skinny body weight. I think if you aim to eat 1800 cals a day you should be off to a good start. Also make sure to eat a lot of protein. Lean turkey slices, canadian bacon, and frozen chicken breasts are excellent for this. Whatever you do, though, don’t starve yourself. Your exactly right, you will lose all muscle but no fat. Your body will burn off all the muslce and then when it has used the source, go into a shutdown state in which you are very mellow and tired to save energy to store as fat. Technically, it can’t tell the difference between voluntary starving or if your in another holocaust.
Along with the food you will need to exersize. I recommend two full body lifting routines per week. It really doesn’t matter which but keep moving, don’t rest for 10 minutes between exersizes. Rest 1-2 at the most. Also, 2-3 times a week, find some type of arobic exersize to do. Go running, biking, or join a martial art class. I’m sure you can think of something.
Good luck. Send me a private message if you have any food calorie content or nutrition questions. I’m good at those.
Try calorieking.com for nutritional info. And so you don’t get to confused about meat, 3 oucnes of meat is the size of a deck of cards.