I have a sharp pain in my left side when I take a deep breath.

Hello, I noticed about a week ago I had trouble taking deep breaths w/o having a sharp pain on my left side.  It went away for a few days, but is back again.  I find myself short of air and feeling the need to take deep breaths, however it feels like I cannot take the full deep breath that I want.  It is not excruciating pain, but it is definitely uncomfortable and painful.  It is below my left ribcage, but not underneath it (if that makes sense).  Basically where my ribcage ends is where the pain begins.  I do have an awful diet(fast food) and I do smoke.  I am 29 years old and I fear that it is something serious.  Anyone have like symptoms or know what it may be? Or how to treat it?  I obviously will go to the doctors if it doesn't go away or gets worse, but with the holidays and work, I have a hard time to get free time to go to the doctors.  I've been told it could be gas, a slipped lower rib, gull bladder infection, collapsed lung or a sore or pulled oblique muscle.  All but the first and last seem very scary to me, and I doubt it is the sore oblique because I havent done very many strenuous things lately.  Any insight will surely help.  Thank you and Happy Holidays!