I'm beat.
I'm exhausted.
I'm pooped.
I'm worn out .
I'm done.
I'm sleepy.
I'm spent.
I'm flat out tired.
I'm dead on my feet.
I'm running on empty.
i'm running on fumes.
I'm fatigued.
I'm tired out.
I'm weary.
I'm dog tired.
I'm tired to the bone.
I'm knackered.
I'm dragging.