Most Helpful Girl
This situation seems more like she was going to cheat and found a way for you to be okay with it.
Having an open marriage usually is discussed before marriage even happens. Not suddenly so one of the peeps can run out and f someone else.
If her whole demeanor towards you has changed and she no longer feels like your wife, then this is the beginning of the end
Most Helpful Guy
When a female proposes an open relationship or marriage. She is already cheating on the man she is with and most definitely does not want to sneak around and hide it anymore.
Men are divorce raped all the time in divorce courts and family courts. So do what you can to look out for yourself legally. Depending on the divorce laws of where you live it may be too late for you but you can still do damage control to minimise the fallout.
If not you could end up losing everything including your house and having to pay for the home that she moves her boyfriend into.
You are a cuckhold. May not want to become one but this is what your wife has done. If having an open relationship is what both of you want and is beneficial then should have embraced the swingers lifestyle.
You should find some dignity and self respect for yourself and do what is in your best interest going forward.
She is only with you for the financial or other benefits that being married gives her. But women don't have to be married to men anymore to have access to their money - resource - property etc... that is why Alimony divorce settlements are so lucrative.