The size doesn't fit. Because the underwear is worn for too long, the bottom circumference loses elasticity, or the underwear size is not accurate, and the underwear runs because the size is not suitable. Sleeping on one's side refers to sleeping on the left side of the body, or lying on the right side, with the fingers on the left side upside down. Because of people's different habits, there are many kinds of sleeping postures, but there are three basic postures, namely supine, prone and lateral lying.