I Have Very Hard Time Breathing, Very Short Of Breath

I have very hard time breathing, very short of breath to where I feel like my lungs are squeezing, usually happens when I'm laying down at night, when I think about it, when I'm excersizing. I've had this for 5 years now, I went to the hospital once because I couldn't sleep and it was very hard, and they just said it was because of "stress" I was only 14 then and is worse now