I have just had my baby now two weeks old. My cat is a year old and up until half way through my pregnancy used the litter tray fine. Suddenly he started peeing all over the carpet and the curtains in the front room. Next the bath, baby bath, suitcase with pillow, laundry basket etc. The litter tray is clean but he will not use it. We shut the cal flap at night to prevent other cats coming in. I have washed, cleaned and scrubbed the things he has peed on many times. I even bought the urine off spray to remove the urine smell and he still pees in the same place. I would be most grateful for all your ideas and help is sorting out this problem.
So he started doing this when you were still pregnant? Before the baby arrived?
If it had been only after the baby arrived then I would just say it was stress due to the upset of everything changing and would recommend Feliway. If it started when you were still pregnant then I've no idea. Feliway is still worth a try though.
If you are using ammonia containing products to clean this will be making it worse. Biological washing powder is the best stuff. The way your cat sees it is an alien has invaded your home and he needs to mark everything so the alien knows it belongs to him. Feliway should definitely help.