Ok lots of people have given you great advice. Please don't mentally beat yourself for one bad day, we all have them that's why so many women diet their wholes lives we just can't seem to get the balance right because we put everyone else first.
Firstly go get an easy cookbook some like Jamie's ministry of food or the hairy dieters. DO NOT Buy a nigella! Then meal plan, I'm a crap cook too but it's easier if I don't have to stand in front of the freezer thinking about what to have when I'm already hungry. Once I start to feel hungry it's all over for me and I have to cook something quick, easy and usually unhealthy. Secondly make sure you prep your dinner early,it's easier to cook it if all the hard work is done plus if you've everything ready to go then ordering a takeaway defeats the object. What helped me was thinking you can have a takeaway but make it at home. Even a homemade korma is healthier than takeaway. We never stopped our Friday night takeaways we just made our own pizza, Chinese, Indian etc
Once you've planned your weeks meals if you can, shop online, it's less tempting to go off list if you are not in the shop seeing the nice but naughty stuff. Don't buy it. If you have a corner shop snack habit put pjs on as soon as you get home at night so going back out is a faff. Even so far as putting shoes upstairs will give you time to talk yourself out of a sugar craving.
Link your Fitbit with my fitness pal and record everything. Also with your Fitbit, 6-7000 steps is a great start but not enough to lose weight. set yourself challenges. Sorry if it's mean but on an inactive day I do over 10000, if I go for a run or to the gym I generally do 20000. Can you incorporate more walking? Maybe borrow someone's dog? it's such a great exercise when you are overweight as it doesn't stress the joints. Can you go swimming too?
Clear out your cupboards, do it tomorrow. The children will not suffer if there are no treats for them for a while. A friend of mine lost 8 stone last year. She now takes her children out for an ice cream if she wants to treat them. It feels like a special occasion and they love having that time with her. She can now control herself enough to allow small bags of sweets into the house but she still won't buy multipacks or family size bags and it took her a long time to get to that point.
If you have a sweet tooth I find melting a spoon of Nutella and peanut butter in the microwave and dipping Apple into it gives me a chocolate kick without being too naughty and gets some fibre and vitamins in too. If you need to snack in the evenings I used to have a small bowl of cereal, something biscuit like like crave that I could eat individually with my fingers. It feels like biscuits, it has a bit of chocolate, It's not healthy but it is better than the alternative.
Please have a look at something like parkrun or join a walking club, runners are all very nice, non judgemental people and it will give you a healthy support network if you don't feel weight lose clubs will help you.
I'm sorry that it's a bit of an essay but I've been where you are, I know how horrible it is to feel so helpless against your own body but now I'm a size 10 and I lift weights. I'm doing a 10k on Saturday and I'm signed up to a marathon in November. What worked for me was finding a supportive group of active friends and making these tiny eating changes. My weekends used to be sitting on the sofa eating as much crap as I could carry home, now because I feel fitter and because TV is crap without snacking I want to be out doing something.
Please pm me if you need to talk like i say I've been there, I know just how you feel, it took me 10 years to find a way that worked for me and I can't tell you how many binges I must have had in that time. Don't give up. Tomorrow is another day and another chance.