Sounds like vertigo. I get it a lot nowadays. The first time I had it I thought I was dying and had a brain tumour or something because the sensation was so strong. Sometimes I feel like I am just gently swaying and then other times I get what are called drop attacks, where it literally feels like actually grabs me and pushes me onto the floor and I do actually end up on the floor because of it. I get the swaying feeling a lot when I am lying down. I sometimes grab onto my bed for fear I am going to roll off even though I know I wont.