I think that often times we get discouraged when we aren't successful at weight loss the first time. Now that you live on your own, you are in charge of your own life, and you should make that a healthy life. My husband works 12 hour shifts, and he is often "too tired" to exercise when he gets home, but we found something that he enjoys to do. He really likes to do yard work as a form of venting and release, and it is great exercise.
You are very young, and you should think about changing to make healthy choices. The first step is the hardest especially when you are tired and frustrated, but eating right and exercising will give you more energy and motivation!
Just try to form new habits.