I Just Don't Understand

I am so confused right now. I ate a kitkat today, the two finger one and i feel sooooo guilty. But why? Because some people eat that just as a snack when i ate it as just my dinner. I felt guilty because it's chocolate and has a lot of calories and fat for something so small. But the thing i don't understand is that, why should i feel really guilty about that when i could have binged on a whole pack of 9. I should be proud of myself that i just ate one and said that was enough. Instead i have to torture my mind over and over again that i shouldn't of had it. I should of just chose a orange instead.
I feel like i have to do 200 crunches.
I feel so tired and have had alot of headaches lately. I know this is happening because i'm not eating enough. But i will do anything to be thin.
I think that i need to plan my calories for the day so then i know exactly how many i have had.
I'm going to go to the gym tomorrow, so that should help this weight loss a little bit faster. I haven't weighed myself in ages because i am so scared of what the scale will say. It's so weird how that little object is so powerful.
I was also so strong yesterday, i took my little sister shopping and treated her to Macdonalds but all i got for myself was a diet coke. No food, just coke. But i was a little naughty and had 2 chips but whatever....
Hope you lovelies are doing well. I am thinking of you x x
Love Logan x x