I recently experienced my first serious polyamorous breakup. My heart is broken, but it taught me what to look for in nonmonogamous love.

• I dated my high-school boyfriend, who wasn't experienced with polyamory, 10 years after breaking up.
• He broke up with me for his new girlfriend, who wanted a monogamous relationship.

I've been polyamorous for five years, but besides my nesting partner — a term for your live-in partner in a poly relationship — I'd never had any other serious relationships in parallel until September 2020.

Midpandemic I was chatting with one of my friends, who also happens to be my ex from high school from 10 years ago. He mentioned he was dating two girls at once. My attraction to him never faded in the decade since things ended, and his openness to dating multiple people at once piqued my interest. And while I got heartbroken, I learned a lot in the process.

Our relationship was real, but I couldn't shake the feeling I was a temporary girlfriend

We began dating even though he wasn't polyamorous. He didn't mind that I had another partner, but he ultimately wanted his own nesting partner. He agreed to research polyamory and see if it was a lifestyle that might fit him long-term, but I worried our relationship would be put on trial with every new girl he saw.

We dated for 15 months and called each other boyfriend and girlfriend. I stayed at his house often and befriended his roommates. He came to my home and played video games with my nesting partner. I spent quality time with his family. We went on a long weekend trip together.

Our relationship this time around felt more impassioned than it had when we dated as teenagers, yet something always held us back. We never said, "I love you." I never surrendered myself fully to the feelings, because I was scared. The weight of the relationship he desired, one that was different from the one we had, hung over us like a shadow.

I wanted him to be happy, so I encouraged him to date. I tried to push him toward the nonmonogamous dating app Feeld, but his experience on it was lackluster. He ended up finding someone on another app, and, of course, she wasn't polyamorous either.

Everything between us changed once my ex found his new partner

At first his new girlfriend was OK with him seeing me, but then he stopped calling me and planning visits like he used to. I tried to talk to him about it, but he refused to see the effect it had on us and was certain that any differences were due to outside factors. I asked him for a commitment to me and our polyamorous relationship, but he just wanted to wait and see.

Our lines of communication eroded as I resented him for his denial and closed myself off emotionally to mitigate my heartbreak in our probable breakup. Sure enough, his girlfriend eventually wanted monogamy, and he chose to pursue that with her, ending his relationship with me.

I've been reeling from the heartbreak for months as I've tried to open up and allow myself to feel what I had blocked myself from when we were together. The bright side is that even though things are strained between us right now, I know our friendship will live on. We made it through our previous breakup, and I know we'll make it through this one too.

Overall, I learned some powerful lessons. While it's great to meet people who are open to polyamory, it's important to align on relationship structures before pursuing something serious. My ex told me from the beginning that he was unsure of the lifestyle, but instead of hearing him and pulling the reins, I blamed him for not committing to me. Now I know it's my job to see the relationship for what it is, not what I wish it to be, and assert my boundaries if I'm not getting what I need from a partner.