What Causes Shortness Of Breath During Sleep?

I'm a 28th year old female. As soon as I fall asleep I would wake up screaming trying to breath coz it feels like I lost my breathe. I had a sleep study done and didn't find anything. It doesn't matter what position of sleep I do. It's always as soon as i fall asleep. Also I cough when I breathe in cold air but a dry cough. Please help me what kind of tests should be done.