You could be getting 'low carb flu'. I got this and it knocked me for six for a couple of days. It is your body adjusting to a low carb diet. You feel very low in energy and ache like you have flu. It will pass!
I also found, in my first few weeks low carbing, that I got really crampy legs when I woke up. I never get leg cramp so it was a real shock. I read a few blogs by low carb people and it seems it is a definite low carb diet thing. A suggestion I followed that helped was to increase salt intake a little and eat a banana now and then for the potassium. I have a banana twice a week. Doesn't seem to hurt the diet and the cramps have gone.
Not had any itchy head so can't help with that!
Obviously if the symptoms get worse or don't clear in a few days see your GP. It could be totally unrelated to the diet.
As for not losing weight, a couple of things could be happening. You may actually not be eating enough so your body is going into starvation mode. It doesn't know you are dieting so if you're limiting food it thinks you need to hold reserves. You may also not be having enough fat. Your body needs fuel. If it isn't carbs it has to be fat. So add butter to veg, use double cream and full fat Greek yogurt every few days, pop a little olive oil on a salad.
If it helps this is my diet for the past two days (I was on holiday recently and went off the rails and have lost 2lb this week). It may help you see whether you're dieting too fiercely.
Monday
Two rashers of back bacon, mushrooms and a poached egg
Roast chicken leg with skin on and a large salad with cider vinegar and salt
Meatballs in a tomato sauce with grated cheese on top with a large salad with vinegar and salt
Strawberries and double cream
Tuesday
Two sausages and a large handful of cherry tomatoes
McDonalds chicken and bacon salad with balsamic dressing and a diet cola
Three of the remaining sausages with tomatoes, cauliflower and green beans with butter on veg
A banana and two squares of 85% cocoa chocolate
Drinks were tea with full fat milk, coffee either black or with double cream and lots of water. I have a glass of water with every hot drink just to negate the diuretic effect of tea and coffee.
I don't know if you use them, but the diet I follow recommends using ketostix. They measure if you are burning fat (ketosis) or carbs. It is a crude measure but if you use them and are in ketosis and still not losing weight you can look at hidden carbs, not enough water (the stick will be very pink, almost at the top level of the scale provided in them) or amounts you're eating.
Hope that helps