try SHAKING a can of pennies at him, i know NO cat who likes loud noises. and isolation could be a very good idea, as long as you're not like me and feel bad after2 minutes and let them out. if you DO have issues with him err...going on the bathroom floor, then get a little spare little box for him (which is also a good idea anyways, in case you have to isolate them due to sickness, etc.). i still think it could be baby. even if it happened BEFORE he was BORN, i know cats can "sense" when your pregnant, so that honestly could be it too. but yes, i do advise isolating him, until he quits, and shaking a can of pennies at him (plastic wal-mart or albertsons bags work just as well too).
good luck!
dionne