Polyamory, at least in terms of sex, is part of my sexual orientation. I don't know if that's because I own and revel in the term/concept or if others feel that way.
So if you're poly and not sure how to approach it, I'd ask you a related question. Would you decision be any more or less difficult if you realized you were gay? Would a lifetime of hiding your true sexuality from others be fulfilling to you? And more so... would you consider your relationships as loving as they are now if in order to keep them, you need to hide something as big to you as your own sexuality?