What Causes Heaviness In The Legs?

I have had many things I have been looking into medically lately and for the past 3 years my legs have felt heavy and like jello at times. Not until 4 months ago did my neck start feeling tight and pressure in back of head and if i am laying down I can feel as if my body is waving like a flag even when i am sitting down or laying down. I need to know whats going on as this is scaring me. I have been told by my doctors that I either have spinal stenosis and that in my neck I have degenerative changes in my neck...what to do next