your goin about it wrong
there's good fats you should eat to stay healthy (unsaturated, monounsaturated...) just avoid fast food basically
and being skinny isn't healthy... having a bit of fat on you is good for you!
I'd hazard a guess at you being medically underweight if that's what you weigh.
I'm the same height as you and 10 and a half stone, I go to the gym twice a week and eat fairly healthily.
What do you do at the gym OP? Why not start running outside or swimming instead for a bit? You are underweight. You should aim to eat more, especially healthy fats found in nuts, seeds and oils and oily fish such as tuna, salmon etc.
You probably aren't eating enough at all. Are you M or F?
If you're 'constantly tired', you are fretting about your weight even though people say you're skinny (and I'd say you're probably too light at 8 and a half stone for 5'8'' - a girl who is fit and in good shape at 5'8'' would be 9 and half to 10 stone easily, and a bit more would be fine) and you have the urge to binge eat chocolate, I'm going to hazard a guess that you're not eating enough.
Start focusing on making sure the things you eat are healthy rather than limiting the amount you eat, and try some new forms of exercise. I refuse to believe that there are people for whom there is no suitable sport that they can enjoy.
keep up the good work as you dont want to get fat
if you stop you will get fat. then you will be having regular visits to the doctors.
which do you want?
hospitail visits or good life feeling good about yourself
if you dont like gym exercise take up a sport or something
like regular kickboxing or football. that will keep you healthy