Originally Posted by MonoVCPHG
Do not let him put any of this on you. Work with him if the relationship is worth it but protect your health. Be loving but don't be manipulated or convinced that your monogmay is wrong. Get counselling for both of you and seek out support for yourself - not just here, but real people to talk to.
Ditto what Mono said, but definitely this. The "real people" should be a marriage councelor.
Your situation is very similar to what nearly ended my marriage last year. The secrets and lies will have to be addressed, they can NOT just be swept asside nor excused. He will have work to do before he can earn back enough of your trust for you to be able to accept him for who he is. He may have figured out that he was poly a while ago, but he didn't bother to keep you informed as he came to his conclusions and in turn decided to keep it a secret and carry on behind your back.
I would tell him that you are not ruling anything out at this moment, but the two of you have a lot of work ahead to repair the damage of his secrets and cheating (and likely will discover also many issues that need dealing with) before you can accept what he is asking. You should also do a lot of reading here and the xeromag site
. Talk to him about some of the things you are reading about. Start marriage counceling immediatley!