I think you need to speak with her about open communication rather than an open relationship. If you're fine living with her as a good friend that also pays half the mortgage then I guess it's ok, if not then you have a huge house situation to talk over with her. I wish you the best.

What's the problem? Get the new girl to pay 1/3 of the mortgage and utilities and $ave $$$. Winning!

If you’re on and off with a person, it’s generally not a good sign to get married to them

Lots of guys would be glad at the prospect of being married to a lesbian couple. Congratulations on living the dream.

Well just because she is seeing a girl doesn't mean your relationship is over. Have you talked to her about it or are you guys all just roommates then? I have heard of situations like this where the wife does have more than one type of relationship. If you still love her I think you really should give it a try to make things work. If you are just roommates then its time to try and find another women in your life.

That sounds like a nice threesome, good luck