"How do I know
?" I don't anymore. Over the last 3 months I've become more aware that it seems uncomfortable for me to be in love with more than one woman. As Mono writes, it's not a matter of self-control or denial, it's an internal circuitry of some kind.
There are lots of electrical switches available. Some let you select a single signal path at a time -- you can listen either
to your radio or
your CD player or
your MP3 player. But not all at the same time. Some selectors let you use multiple sources: you can pipe your electric guitar and
your dub box and
your drum machine into the same recording line. Simultaneously.
This is a really crude analogy, but it feels a little like that to me. Some people's love-switches accept multiple inputs. My internal switches only really accept one love at a time. (It's a really a poorly designed switch, too, because there's quite a bit of arcing and burning when it has to change to a new configuration, and that hurts.
But I'm lucky: I don't mind if the person I love has the other kind of switch. I can love someone who is also in love with other people. That's really great for me, because I can get the benefits of compersion and wider relationships even though I'm not completely poly. And I don't seem to suffer the terrible pains of jealousy and anger that sometimes go with the full mono configuration. Whew! What luck.
I don't really believe it's as simple as the switch analogy. People are damned complicated, and emotions are extraordinarily complex. The ideas of situational sexuality, serial non-monogamy, and relationship webs do a better job of showing some of the complexity.