It may be that your blood pressure is dropping when you stand up or stretch. You might want to mention that to your doctor.
What could be the causes for feeling dizzy every time I stand up or stretch? I have had a blood test to see if I am anaemic and I am not. I sometimes feel dizzy when lying down as well.
Sounds like a symptom of a blood pressure problem .. Only a doctor can diagnose that.
You should be checked by a doctor, but I would like to point out that there is a balance mechanism within what is called the "Inner ear".
This balance mechanism can be temporarily impaired by a viral illness, and when this occurs the condition is termed "Labyrinthitis".
You can view more information about vertigo here:
I hope this helps, and that you feel better soon.