Speaking from experience... it's a hard habit to break. But figuring out how much you're actually throwing away on eating out is the first step.
Breakfast is pretty easy as you've found. Lunch isn't too bad either. There are always sandwiches -- I hope you can make a sandwich.
As far as dinner is concerned, you don't have to start from scratch. Start with something like frozen pizza -- buy a Jack's cheese pizza and cut up tomatoes or mushrooms or whatever you want and put it on top before baking it. Boil pasta and throw in Ragu. There are lots of things like this.
As you get more confidence (and get bored with those meals), you can get more creative. For example, instead of Ragu, you could make your own pasta sauce.