Maybe it's inappropriate for me to comment on this, but I agree with the responses you have gotten so far. As I've told you, I don't feel we can control who we are in a relationship with and it is very restricting to try to label one or all of them. Look at my relationship with C - we've never questioned where we stand in each other's lives. Our love has always just been a fluid partnership and whenever one of us has something or someone else "come up", we treat each other with respect and support. I love that about us. When she met you the first time, her comment to me was "Loving you makes me WANT to love other people."
I also agree with nycindie saying that I shouldn't be the only one setting parameters - which obviously I am not, but I do feel as if I am the more aggressive out of us. I think I am just stuck in the struggle between being sensitive to your needs (and other peoples' needs as well) and being sensitive to my own. We will figure out what works for us.