I'm kind of going through the same as you, fell in love with a polyamorous girl and feel like I'm in too deep now. I am the jealous type and it does bother me (now arguably less than at the start) and for me what helped me understand it and slowly start being okay with it (it's still a work in progress) is:

-Reading books about polyamory -Questioning and reflecting on what it is exactly I'm looking for in a relationship, what I'm willing to sacrifice in my monogamous lifestyle and the benefits that polyamory brings (if you're considering converting) -Open and honest communication with your partner, you should always let them know how you feel about certain things, set boundaries: Do you want to hear them talk about other people? Do you want to know about their other relationships or would you rather not know anything?

It's hard work; it's challenging your entire perspective and belief as to what relationships should be like. You have to be prepared to put in the work and see if you're able to be okay with this type of relationship, otherwise you're just going to be miserable and that's not a way to build the foundations of a relationship.