Inflation In Lungs. Breathing Issues. Non Smoker, No Asthma History. Meaning?

trying to find out why I have been experiencing breathing problems off and on for a year. They come on suddenly and last for weeks.

Then disappear. Once gone I am normal, working out all the time, biking to work ect. I don't feel out of breath as much as like i am yawning and trying to get air in, like I don't have enough.

I am a non smoke (Had the occasional cigarette in college at parties in the summer, maybe 10 a year).

All xrays have been clear , last showed slight inflation in lungs. 29 years old, female. Also no history of asthma though i have smaller lungs since I was a child.l