pain and heavy feeling in my chest.... ? causes?!

I keep getting this pain and horrible heavy feeling in my chest... it's on the left hand side, I have been to the doctor and she has done a whole bunch of tests on my heart and everything is fine there, she says she can hear some 'wetness' when she listens to my left lung when I breathe but has no idea what the cause is and I am constantly feeling like i need to cough or clear my throat but it is very hard to clear my throat or chest and usually requires alot of hard coughing... what could be the issue here? I am seeing my doctor fortnightly and we are trying to get to the bottom of all this but I am just looking for suggestions on what this could be? oh I guess i should mention that I also often get pain in my shoulder...