A lot of weight loss is being in the right frame of mind. If you keep telling yourself that you're not sure if you'll be able to do it, you probably won't be. No one else can give you the motivation that you need to actually do it. You're going to have to pull down inside yourself and find that. You say that you want this more than anything else, then it's time to make a commitment to yourself to do it. Make a commitment to start eating healthier right now. Create that controlled environment for yourself. Get rid of the chips and microwave pizza. Go grocery shopping for healthy foods to take their place. Use your free time to prepare snacks, meals for times when you're too busy to cook. Start today. And if you slip, like we all do at some point, pick yourself right up and keep going. Don't let one bad meal or snack turn into a day or week of bad choices. You CAN do this, and you are worth making the commitment for.
I have heard others say and I have said in the past "I would do anything to lose weight". And the simple reply is "Would you watch what you eat and exercise?" It seems so simple, and it is really. You just have to start by getting past all of the negative thoughts in your head and know that if you commit to doing it, you CAN do it.