eeek! Is it too late to put the preggy plans on hold until you sort this out?
his other woman and I are both monos- and if he knew he would have looked for poly friendly women-
Sorry but this is rubbish. If he thought you were poly friendly he wouldn't have kept the other woman a secret. He is being cowardly and now he's trying to justify his actions.
Check out my blog (link in signature), It's all about I dealt with being a mono in a poly relationship. I now consider myself poly friendly but you can only get to that place with honesty and your man needs to find some in a hurry.