My left chest hurts when i breathe in deeply

It doesn't happen all the time, just rare occasions but when it happens it hurts like a bitch. During the pain it also hurts when I widen my chest or tilt my head up. It feels tight and like something is twisted inside. Usually I just take small breaths before taking 1 deep breath to make the pain stop and it usually stops. I'm 21 years old by the way and have stopped smoking for about 5 months. Hope someone can tell me what's going on :)