Try doing a search in the tags for "secondaries" or "primary" or the like here and many conversations will come up.
Generally speaking, primary/secondary for most established poly tribes is more about financial commitments, children, shared assets and time. Partners quite often become equally loved for different reasons. You are in good company with that. Sex partners for casual sex are quite often secondary or just seen as good times and the sex being about sport. Love to me and it seems most poly people, is always primary.
For me? I try and keep myself primary and put my self first. I think self love is the most important, everyone and everything is secondary. That doesn't mean I'm egotistical, just aware of my self and my needs as being priority. I keep in mind that my needs also require that I have to be considerate/compassionate/empathetic and be a good team member or no one will want to be around me.
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