What can cause a retracted eardrum?

I've had a retracted eardrum for over a month now. I went to my Doctor and he confirmed what I thought. He also said that my ear is clear inside and that there *isn't* a perforation on the eardrum.

In my case, what could be the possible cause of an eardrum retraction? And is it likely that it will fix itself?

[bsmsl]

Did you doctor say anything about eustacian tube dysfunction?  This is typically caused by swelling of the membrane from allergies or other itritants.  It keeps the ears from equalizing presure as they normally would.

You can try using Afrin for three days and then not using it for three days.  NO MORE THAN 3 DAYS OF USE AT A TIME.  Afrin has an addictive like reaction which results in rebound swelling of the membrane tissues causing one to feel even more congested.  If this doesn't work, I suggest you see an ENT for further evaluation and recommendations.

Take care.