Thank you for the perspective, FireChild and redpepper. I'll definitely do better searches for similar posts.
redpepper, you bring up another concern I left out - that casual sex isn't poly. Kamala just posted something about this issue, too, but so far no replies. Like her, I'll keep an open mind, and while my boyfriend supports my pursuit of other love relationships, maybe he isn't poly ... Anyway, I'm sure I'll end up chalking this whole experience up to an "experimental" phase.
Thank you for the responses and support!