I think that people who suffer from anxiety tend to be more "in tune" so to speak with their bodies. You notice something that ordinarily would not even cause you to blink. This then leads to more thoughts and more "in tune" times. I agree with mammo that you have nothing to be concerned about as far as the numbness in your scalp goes. Think about sitting too long, what happens to your rear end? It become a bit numb.
If you find that you are worrying more and more about your health, then I would make an appointment with your health practitioner to discuss what you are feeling. You mentioned a CT scan 6 months ago and so something at that point must have been bothering you. It could be that these are anxiety symptoms but you would have to discuss this with your GP and go from there.
All the best.
I wouldn't be. It sounds like you may have been sleeping in a position that was pinching a nerve, especially since it went away so quickly. It happens, especially at night and is nothing to be concerned about. I wish I had a nickel for every time I woke up with something being numb or asleep! LOL