Under arm pain on the left hand side was what started me off with health anxiety , things slowly progressed to neck pain , burning skin etc through worry etc etc etc .
Had loads of blood tests as the lypmh node was enlarged for months , i had a scan at the breast clinic (only male in there
) , like yours it was normal . Underarm pain can be caused by muscle tension from the chest (my doctor explained this) .
I still get under arm pain now but i just ignore it , its been there since August 2010 so i give it no head space . If you have had a scan by all means see the Dr but i don,t think you have anything to worry about