I don't know why this is, but for the past month or so, I've been having trouble falling asleep, periodically, because it becomes hard to breathe. During the day I am fine and it is only at night, when I lay down, I start the breathe in, but I can't feel enough air coming in and I hear a whistling noise. I am 18 years old and I've never smoked. I recently had a blood test done, and everything seemed fine. I am not overweight and don't have any problems that I know of. It doesn't happen everyday, but it's been happening a lot lately. Once I get up out of bed, I can still hear the whistling noise, but breathing becomes a bit noiser. Does anybody know what this could be?