Thanks for query,
It seems that you might have Postural Hypotension
Now do one thing,measure your bp 1,while lying down and 2,in standing position.
If there is much difference in reading it show posural hypotension.
From sleeping position you slowly come on seating position and then slowly stand up.
This will prevent you feel dizzy and lightheaded.
For bad muscle cramps
you might have some viral infection.