ALL iTunes backups are CORRUPTED. HELP!

Ladies and Gentelmen -

Here is the situation:

I owed an old 3GS. I sold it on ebay. I connected it to my iTunes (which was set up to my iPhone 5) to wipe the 3GS, which it had not been wiped before I sold it. By doing this I had no idea I was going to create a problem for myself...

A few days later after experiencing some issues with my iPhone 5 with cache memory and trying to use the search function on sms, I decided to wipe the phone and restore from backup. Simple enough right? and straighforward...

Well, when I tried to restore from backup I notice that the most recent back up was corrupted. I tired other back ups in itunes and all of them where "corrupted or or not compatible with the iphone that is being restored."

I have tried 'ibackup extractor' as some other forums suggested and it still does not work. I have called apple care and did could not help me.

All I am looking for is to resore my iphone 5 back to where it was 5 days ago. Images, sms, notes, etc.

Anyone has any idea what in the world happened? Is there a way of resolving this problem?

Thanks everyone