Something happened last night.

I was laying on my stomach in my bed, my mind was clear. I don't have to do meditation, my mind is usually clear. So anyways, I begin to drift off into sleep, when BAM! It feels as if the bed was yanked out from under me. I felt like I was falling very rapidly, but then all of the sudden it stopped. I didn't move or anything, it just gradually stopped. I observed that my body felt very heavy, particularly around the leg region.
What will I do? I fell asleep a few minutes after this. xDD