Struggles With Nonmonogamy
So my partner and I have been nonmonogamous for about 4 or 5 months, we have been together for a year and a half. She initially brought up the topic this summer because she had been feeling guilty about having attractions to other people. I agreed to open up our relationship because I wanted her to be able to be honest with herself and not have to hide. We have struggled a lot (mostly me) throughout these past months getting over jealousy hurdles and insecurities. I definitely have not conquered the two of these powerful feelings, but I have gotten a lot better. Recently, though, I have been having doubts. From the beginning, I did not want to be nonmonogamous, I only did it for her. I thought that I would feel differently after some time passed, but it hasnt at all. In fact, it is really starting to affect me. I feel like I'm lying to myself and my partner. I feel so stressed every day and I usually break down and cry on a daily basis because it is too much for me to handle.
So here is my predicament: I want to be with my partner. She means the world to me and I never want to lose her. She is nonmonogamous and I am monogamous. I don't want to ask her to be monogamous, because that wouldn't be true to who she is, but at the same time, I don't want to be nonmonogamous because I don't feel that it is true to who I am. I am at a complete loss as to how this could be resolved so that everyone can be happy.
Please lend me some advice