Single Parent Support

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I'm a single mom, I work full time and am a student. I live in a area where I have no family and no time to really make friends. I'm about 5'5" and weight a good 240lbs. I've been trying to lose the weight but keep falling off the wagon. Mostly over food and time. I'm a avid cook but it seems like I never have time to plan anything healthy or count the calories for a meal. And at the end of the day between getting my four year old to school and daycare, cleaning, studying, and work I'll head to work at night and realize, "oh my god, no lunch...look there's Arby's!" Do you have any advice or methods you use to make more of a organized effort with food, how do you count the calories for a recipe when you cook by feel not measurements? How do you find time to work out when it seems like there aren't enough hours in the day?