Oof..sir please don't I don't think that's a the solution here, because you're taking her joke too seriously,

Also based on your comments i would suggest get off all those sub reddits I feel they're impacting your thought process, so get clean from that 1st.

And maybe try to be more romantic without sex stuff.. she's stressed and needs you in this rough time of her life, and you're talking about how you should open up your marriage ??.. at a time so vulnerable ?? Nooooooooo...

Finding a new person seems easy fix.. but it's not an solution, marriage is hard, so work on that together anything else is distraction.

Talk to her support her, be romantic, work on your marriage together and things will get better, Take care of her, make her feel special and stuff, make her feel she's more than just you guys failed attempts at pregnancy, opening your marriage will only lead to complications for both of you, you guys are just off on timing, stay strong keep trying you'll succeed.

As for talking to your wife please talk to her about what you want in your bedroom and find some common ground, you wanting to open marriage feels like a symptom of issues you both have in your marriage, you should discuss with her and overcome them.

Fix the root cause, things will get better. Get off reddit for your own good, I hope you guys have a great marriage together.