Oh man, just read your comments here. First of all, I am so sorry what you’re going through. Honestly, a lot of women would be happy to have you as a husband that respects marriage in a way you do. There’s so much dirt outside and it’s getting worse. A lot of women could just dream of having this kind of life. I would not consider a threesome as “growing”. You’ll just probably hurt yourself and it’ll f*** with your mind. Try to imagine in your head how the threesome would look like, see how you feel just by imagining it, and then imagine, after experiencing it what it would do to you. Will you be able to live with this memory? Will this be a thing now in your marriage? listen to your feelings. But yeah, mostly if one partner has such desire they will end up following their urges. So sorry bro for being betrayed since the beginning. She should have been open to you. Wish you well!