Well hi! You weren't by any chance in ATI, were you? Your religious background sounds very similar to mine, and my family was pretty involved in that program. Obviously I'm not involved in the program anymore.
I'm going through a somewhat similar transition in terms of exploring poly and rearranging my religious beliefs. I'm not quite at a point where I would feel comfortable saying I'm an atheist, but I think agnostic is a pretty good description. I guess I was a little lucky in that my family pretty much exploded out of the program when I was 16 due to a really complicated situation, and I've been exploring my own beliefs and sexuality since then.
I don't have anything in the way of advice since I'm brand-spanking new to poly myself, but I just wanted to say hi.