I understand the when one is in orbit, the inward force of gravity at
one's center of mass is exactly balanced by the outward centrifugal
force from the orbiting motion, resulting in weightlessness.

 I want to know what weightlessness actually FEELS like. For example, is
there a constant sensation of falling? And what is the motion sickness
that some astronauts occasionally experience? 

 Please reply only if you are either a former or current astronaut, or 
someone who has had this discussion first-hand with an astronaut. 
Thanks!
