My husband and I started off non-monogamous. He had a girlfriend (long distance and also non-monogamous) and I was his "secondary". I was also in a long distance non-monogamous relationship. And I was dating casually. It was the first time in my life I'd had open relationships as I was a serial monogamist. We didn't call it polyamory because, well, the being in love came later. We fell in love before closing off the relationship. Monogamy happened because his gf was abusive, he'd never been monogamous and he'd never loved anyone like he did me and wanted to marry me. I think we went mono because it was what we sort of expected to do when deciding we wanted to be married and have a family. Years later I fell for a female friend of his and we went back to poly after MUCH discussion, pushing of limits, and breaking from traditional expectations. We formed a V with me at the center and were (I feel) beginning to work towards a triad. That relationship didn't work out and we are again a monogamous couple, open now to poly but not looking. Neither he nor I want me with another man. I don't want him to be sexual with another woman (at least right now, though if we find a mythical unicorn as we almost had that might change). So I'm poly while he's content being sexually mono and emotionally poly. Basically, we've gone through quite a few phases. A relationship almost never starts as polyamoros, just as a couple almost never start IN LOVE. It starts open. The "amory" comes in time. The "poly" can be there from the beginning. Don't get too caught up in labels. But don't start off denying what you are either.
I'd rather be hated for who I am than loved for who I am not.