Why do I get headache while standing?

Hi doctor,

Over the last few days, I have a problem with standing without feeling dizzy. I feel that while I am standing or sitting on a hard surface, that I am in an elevator or a boat. Sometimes it happens when I lay down too. I also feel that there is like a pressure or a wave inside my body that directs the way I feel dizzy. Sometimes I feel it in my legs and sometimes I feel it goes up to my head. I can literally feel it and feel how it is dropping from my head to the body. Every time I feel I will faint, however that has not happened yet, probably because I lay down straight away as soon as it happens. I have panic disorder and sometimes when I feel this I get anxious as I am scared that it may be something serious. Occasionally, I have a slight headache but is not severe at all. A few days ago, I tried smelling lavender and chamomile oil, which is something new to me and I do not know if it has anything to do with this dizziness. I also have dry mouth most days recently too. It has started controlling me as I always need to hold the door or the wall in order not to fall down. I saw my general practitioner (GP). He asked me to close my eyes tight. I was going to fall down if he did not hold me while I was standing. Please note that I used to feel like the floor is moving up and down at night before I sleep. However, now it has increased to the stage where I feel it since I wake up till the moment I sleep even if I am lying down sometimes. The more I am awake, the more I feel it. Finally, when I come to sleep. As soon as I close my eyes, I imagine spinning even though I know the room is not moving as well as sometimes pain is in one side of the head. Your advice would be appreciated.