Could a native speaker help me properly express

Could a native help me properly express these sentences please?

1 Out of all the people in class, it seems I'm the person who's falling asleep the most. (Keep closing my eyes falling dosing off and then waking back up)

2 He stopped moving his leg where it hurt less. He moved his leg around until when it hurt less and stopped moving it.

3 The blister will pop once the skin underneath is hard enough to come into contact with the air. It'll heal slower if not open to the air.

4
Time never flies the way it does when I'm with you.
Time never passes as fast as it does when I'm with you.

Thank you so much