another thing you should look at is your goals. if your goal was to change everything you eat and do this perfect week of exercise, loosen up the rules. if you could eat perfectly and have a perfect exercise regimen you probably would have already been doing it in the first place and you wouldn't have been able to fall off the wagon because that is just what you do. since that's not the case, don't set aggressive goals. if you aren't exercising at all, it's not a great plan to run a marathon on tuesday. if you weren't exercising at all your first goal should be more along the lines of 10 minutes twice a week. if you can hit that quite easily, then try either 10 minutes three times a week or twenty minutes twice a week. and as you get adjusted to that level, bump it up again. and keep doing that. inch up your short term goals with the idea of eventually getting to your long term goals.
and you can do the same with food. if 14 of your meals come from fast food on an off week, making a goal to cook 21 meals from scratch this week is probably going to be a bit much. making better choices for those fast food choices would probably my first goal. keep in mind that most grocery stores have premade salads, parfaits, cut up fruits, soups, and sushi that can be a little better for you than fast food. my next goal would be cooking one more meal a week from scratch. then making sure that when i am cooking from scratch, i am making enough for that meal and at least one more meal. and then making one meal for now, at least one to freeze and at least one for leftovers. and gradually increasing how much i am actually cooking. and doing that will mean i have a list of better choices if i do head out for fast food and i will have a backstock in my freezer of homemade meals.
-google first. ask questions later.