I have googled this so many times but I can never find what I'm talking about. When I lay in bed, sometimes I get this antsy/crawling/jittery physical feeling in my body. Moving or changing positions makes it go away but it comes right back. I'm not thinking of anything really - but I cannot relax or sleep. I normally smoke a little to be able to shut it off so I can sleep. 

Is it something like lower back pain, being uncomfortable, or whatever causing physical anxiety? 

Does this sound familiar to anyone? What is it and how do I make it go away?