One more thought: if you do start seeing a therapist, and after a few sessions you feel that they are not very poly-friendly or are not giving very poly-friendly advice, don't be afraid to seek out a different therapist.
I made a mistake in staying with one therapist for 6 months even though she could not grasp what I meant by "having feelings for more than one person." She could not fathom why I was deeply grieving for the demise of a relationship in which I had wanted to see other people. She kept telling me that I must have Asperger's (I don't) or that I needed serious medication and/ or a full psych exam (which would have cost $2000 beyond my insurance).
Single, straight, female, solo, non-monogamous.