Sounds like you have a lot on your mind. Nobody owns your brain but you though. You can think and learn about whatever it is you want to think and learn about. Knit. Make baskets. Polyamory.
I don't think mere thinking about things is what you are after. Could try to articulate your wants, needs, and limits more clearly.
I'll pose some "thinking cap" questions not because I actually expect you to answer me... but to try to help YOU think it out to yourself in your own head. Then maybe you could try to articulate to wife better what it is you are after in the marriage?
1) You say you "have a good relationship." Does that mean you have a good relationship with her? How is her relationship with YOU? The communication arrow in relationship is a two way street there. She's meeting all your wants/needs in relationship? Are you meeting hers? So you both are harmonious?
2) These emotional affairs -- was it crush stuff? One direction? Or reciprocated by the other person? How have you hurt her? Why 3 times and you keep on doing? What agreement/boundary/limit is difficult for you to adhere to and needs renegotiation?
3) What is it you want/need from your wife? Understanding? Freedom to date? BOTH? What is "active in poly?" Going to educational classes? Dating? Something else? You aren't specific.
Wife might be ok sharing in your inner life and hearing about crushes that come and go, maybe even reading poly materials, and learning about poly with you. That would be the monoamorous spouse Opening to love the polyamorous spouse in full color while sharing a monogamous relationship structure with them. You close down to a monogamous structure to meet some of her needs while she opens to knowing your inner life and polyamorous side to meet some of yours.
That's a different thing to ask for than a "monoamorous spouse + a polyamorous spouse in a nonmonogamous relationship structure."
4) How's your timing on this? It sounds like she is upset with you because what? She just found out about 3rd person emotional affair?
She's also pregnant -- not the best time to be putting all this on the table. Pregnancy hormones make one super emotional. Wife deserves your support and nurture in partnership, and in pregnancy times even MORE care and consideration. Is pending fatherhood (again) giving you wanderlust urges?
Could holiday season be affecting things? Sometimes all the "holiday family togetherness" can feel suffocating. Is there some of that causing strain?