Heartsong!
Your opening post speaks to me. As Al has said, many people come to these forums on a background of a long term relationship that is opening from monogamy to polyamory. It's a difficult transition and only the foolish do not take it slowly.
I would be one of the foolish, by the way. Al and his partner had a healthier approach, I think.
I have, in trying to recover from my initial hurt, explored this topic and read a lot of threads on this forum. I'd like to share with you some links, for you to peruse as you see fit.
There are many factors that can influence a smooth transition from monogamy to polyamory. I think one large factor would be the health of your monogamy. After all, if you can't do one relationship, what makes you think you can do two? I started a (relatively new) thread on a
relationships vulnerability quiz. I think the quiz is designed to be done by you and your wife separately, then comparing scores. I think the difference in scores between your perception of your relationship compared to your wife's may serve to highlight areas of your monogamy that could do with improving. If you find it useful, I would love to hear some feedback about the quiz with the aim of improving it before recommending it to future couples. Thanks.
I also started a
thread giving examples on monogamous couples transitioning to polyamory. The thread selectively showcases those who are still together after a reasonable length of time. Bear in mind, many don't end up staying together and you can find allusions to these in most of the blogs and life stories. Finally, "staying together" may be a goal that monogamous people like you and I cherish, but polyamorous people will warn that "staying together" may not be healthy, and I discuss the polyamorous viewpoint to this in the link given.
Finally, if you're opening from monogamy to polyamory, just be aware that there are
other forms of consensual non monogamy around. Some of these may (or may not) suit you and your wife better and (I believe) many may be easier to transition to from monogamy, whereas a move from monogamy straight to polyamory may be more difficult. Just my opinion.
Best of luck with the new change in life,
Shaya.