Cocogirl dont fret,...the good thing with diet is everything is fixable.
Its sounds like you have gotten so depressed about body weight that you have gone to the extreme to lose it,..which of course works (for ashort time anyway) until you body begins to show signs (tired, weak , lack of focus, mood swings) sounds familiar.
Think of your body like a high performance car,...you tune it up, keep it oiled, lubed and fuel with high premium gas, you drive it well ..it runs nice
You give it low grade gas, forget the oil and lube, run it like crazy it will soon blow its enginge.
NewBride and I had many a talks about diet is not all or nothing. Meaning you are not failing your diet when you actually eat.
One helpful hint is when you go to your grocery store,...shop the perimeter first....that is where your grains, fresh meats, dairy fresh veggies and fruit are. The more colourful your cart the more nutrients are getting in there. The aisle shopping is where you will find more processed foods, high in sugar, starches and empty calories.
Take care of yourself hon!!!!