Hi..welcome to the forum. I don't know how much information you'll get on here regarding FAP. .I've never heard of FAP (Familial Adenomatous Polyposis), did a quick search and initially I'll ask you if you've done family enquiries as to others who have it?
This is an good link with other links that might be able to lead you to more information or other links that might have message boards/forums.
http://ghr.nlm.nih.gov/condition/familial-adenomatous-polyposis
Interstitial cystitis has been mentioned by a few women on here occasionally. Some have it in conjunction with UC, and from my experience of being tested for it, I was relieved it was negative.
I found this site that also may be of help that can get you connected with a lot of information.
http://www.ic-network.com/
It's sad to hear you have two devastating diseases to deal with. I hope you have support from family and friends as well as doctors/medical.
quincy