Since that last post, we've found this girl who seemed perfect for us and really liked us both. I was able to get over the first hurdle of worrying that he would have sex with her, and it was a great experience when we did, but just last night, I became very uncomfortable because he "laid his seed" in her (while I was there, of course). I told him it was ok at first, and then admitted it REALLY made me uncomfortable. But he was so hurt, he felt like a pervert or some kind of bad guy like he pressured me or something.
I spent all day thinking about it, wrote down some very negative things about our triad that came from a negative place, and then I realized the problem is that I'm not as emotionally close to her as perhaps I should be. I felt unequal because I knew he and her were more comfortable with each other than I was with her. So, I'm going to try and get closer to her, so that the next time it comes up, I'm glad to share my love and lover with her. I already respect her and enjoy her company a lot, it's just the bonding that was missing, y'know?
One of you made me realize I'm very lucky to not have a pervy boyfriend who wants a threesome, but a sensitive man who supports me no matter what, in whatever kind of relationship. If it really came to it, he would ALWAYS chose me over anything. But because I love him and I love and respect her in a different way, I want them to both be happy, and to be happy with them. She really does like us both and she's a sweetheart. I think we could all grow substantially from this arrangement. I already know I have!
Thanks all, you really helped!