What Causes A Sense Of Losing Control Over Legs While Sleeping?

i m 47, female, 5 6, 170 lbs and anemic. I have recently been taking a fourth of 0.5 mg xanax once a day maybe every other day. I am now taking integra. When I took the fourth xanax at 3pm i then took one integra at 6:30 pm that night and haven t been able to sleep since. This was a friday today is sunday. Whats happening is when i try to fall asleep a sensation comes over my entire body as if i m falling and my legs feel as if they are coming apart from my body. This only happens when I m falling asleep which then keep me awake for at least 6 hours and then maybe i get 1 hour sleep. I took only the integra sat. and still had the same issue. Today, sunday, i havent taken anything and tried to nap and experiencing the same. I thought the iron may have played a part being anemic and starting 125 mg iron. I m so needing an answer. thank you.