character doesnt fall and sometimes spins around?

ive been making this 3d platformer in unity and ive run into a problem. my character spins around and will float in midair instead of falling down and touching the ground. heres a video:

if anyone knows why this is happening please tell me

 

Well, you haven't given us any details, so you can't get a detailed answer.

But if I had to take a guess, it would be that you're using the physics engine instead of controlling the behavior of your character yourself.