SS can make you a bit light headed if you get up too quickly and will be made much worse if you arent drinking enough water , so make sure you are having at least 3 litres if not more .
It must be the day for it as I did the same this morning. I'd been up about 40 mins had been in shower etc, but then when drying my hair went very feint feeling and had to sit down. If i hadn't I would certainly have hit the deck. Keep trying to drink more water, I'm up to 1.5litres. Just had 2nd pack of the day and starting to feel a bit more normal ...
You are drinking your water? Could it be caffine withdrawel? have you tried a little paracetemol? If it persists you might want to go and see your GP -- just in case. I hope you feel better soon.