Yes I agree not everyone wants that, I don't know where I have said that but I don't believe that, I before, this was important to me, exclusivity of being in a monogamous relationship.
Yes my partner was thinking about herself but did express she thought this would be something I would want, because its been very busy and we don't get a break from adulting, parenting and having time for eachother, it's not how I would of raised it and the way she did, I've expressed that it was unfair, I believed there was something up for 3 weeks and she withheld this from me, this idea.
It's feels it has changed the relationship, I do want to be with her and have the future we had planned before this, but it feels as if she has slept with someone, and I feel this change has made me want to now, but as before and reason why I was upset, is that it takes the time away from partner, family and I made these sacrifices when having children, lots of benefits but sacrifices, knowing that some of my needs and wants would have to be set aside, as I've got to there.
She believes in an open marriage and tried basically selling this to me originally, but I thought of the big picture, STDs and other issues that come with it, Jealousy.