I stayed quiet as my suggestions are not Homeopathic. However, I would try Flower Essences and communication. I imagine this has a lot to do with the fact that you are pregnant - he like your other cats is sensing what you are going through and reacting accordingly. Do your cats not get outside?

There are many excellent Animal Communicators who can talk to your cat and ask him what's going on, this is the lady I use www.talkinghorse.co.uk and once she has had a chat to him, you'll be better able to see what Flower Essences would help most. Walnut would be good for you all, it's for change.

All the best.