Random difficulty of breathing?

So this comes randomly - it used to happen more often but not anymore but it just happened right now. I'll be minding my own business, i'm at rest so its not like i'm doing anything thats gonna make me breathe heavy. but what will happen is it will suddenly hurt to breathe. my chest will tighten up and i can only breathe so little before exhaling. and I usually feel it always on one lung. It can last anywhere from 30 seconds to 5 minutes and its absolutely painful to try and get enough air to breathe. This used to happen a couple times a day but now it's like once a month.