Are you drinking plenty of water, Lauraann? You need to try for 2 litres a day when you are reducing carbs, particularly if you are going quite low (below 70g, I would say), because you can get a bit dehydrated and headachey.
It's not as difficult as it sounds - I have a 2 litre measuring jug, fill it every morning, and work my way through it during the day - a mouthful every time I pass it. If you're at work, take a 1-litre bottle and make sure you get through it, and drink the rest, am and pm, at home. No need to buy it - fill an empty from the tap!
A couple of coffees or teas can count towards the fluid intake, but you do need water.
Viv 8)