Sorry to hear this Booklady
I'm not sure what to say. I'm a lot like your boyfriend when it comes to accepting pre-existing relationships but not new ones. I have no issue with saying I love Redpepper though..hell, I wear a ring on my wedding finger to show people I am "taken".
I don't know how to help really. Maybe he feels he is somehow saving face in his mono mind and in the eyes of other monos by withholding those three words. I get that. Maybe he doesn't expect this to last and is afraid to say the words. I still have a nagging thought about the sustainability of how me and Redpepper express our love. I still wait for the other shoe to drop but I am happy and move forward because I know we will always be connected as family. Nothing we build will be wasted. That's where my strengths and resolve come from.
Can you ever truly overcome mono/poly differences? In my opinion...it all depends on the kind of poly dynamic and what the person's idea of monogamy is. Do I think a mono will can become consistantly happy with a completely fluid open poly partner that they truly love
?...not in my opinion. But I can only speak for myself.