Sai - My husband and I are in the same boat as you. His AP has been pending with the CSC for more than 90 days. We called USCIS customer service and they said that we must wait until our receipt date is 30 days past the date on the "processing times" list on the USCIS web site.
For example, our application receipt date for our I-131 was October 3. According to the web site, the CSC is now processing I-131s with a receipt date of October 18. When the web site is updated to report that the CSC is now processing I-131s with a receipt notice date of November 3rd - only then can we call to report a problem.
Ugh.
Good luck!
Nora