Hi Nan,
You might want to post this in the Ear, Nose and Throat forum:
http://www.medhelp.org/forums/Ear--Nose--Throat/show/70. This is the hearing loss forum. :)
Is this mucus problem new? If so, when did it begin? Was anything happening at the time that might have a connection to it?
Your esophagus cannot be damaged by clearing your throat. Your larynx (voice box) could be. Make sure you clear it gently, also drink plenty of water.