I know what you mean about the sex... and the falling in love. I think the falling in love part it what makes it hard. It's amazing and the drive is so so strong and also hard to stop!!
My husbands best friend and I fell for each other this winter... it's a story of its own (I'll post it soon) but now we are at the 'where do we go from here.' Although you guys are starting from a much better point than my husband and I are in relationship honesty.
Enjoy falling in love!! Keep posting- I am also a woman with two men (both pretty mono men too) and I often wonder, does that sort of thing ever work out for long?