Pinterest seriously helps me! I'm 15 and need a boosts to do that:) make a board for fitness and in the diet and fitness section. You can look me up I have one going that is really good:) my name is Judy Kinch and my board is called fitness motivation:) ou really should! It helps!
I'd start by taking a look at your diet and water intake, if you are dehydrated it's hard to find the will power to do anything. Try and eat healthy for a week or so and keep hydrated, you'll soon have the energy to start doing a bit of exercise, then start off small with a few press ups and gradually increase what you are doing, after a short time you will want to do it because you'll start feeling better about yourself.
Stop being lazy,put your dream before anything else,when you start seeing results,you will thank yourself,but you won't get results just by thinking about it,what would you rather be unhealthy and lazy or pumped up and active?
Try to incorporate it into your daily routine. The less of a hassle it is to you, the more likely you'll keep it. I lost 15kg by running 20 minutes in place right before shower. (coupled with healthier eating)
Work out with friends! Or just find the main reason you want to get bigger. You will work harder then, and it will eventually become fun.