Nicraq, believe me, he and I have been around this topic more than once.
He assures me that if they did manage to get that part of their relationship back, it wouldn't change what he and I have. He assures me that they started down this path while they still had an active physical relationship, but 3 years ago, that stopped. He continued without her, but with her blessing.
The great thing about our relationship is that he does encourage me to tell him if something is upsetting or bothering me, and he will and DOES help me work through it. We can talk about anything... unless it's her passive-agressiveness towards me, that's off limits, he gets too defensive. In his eyes, she's perfect, sick, sweet, angelic, do no wrong. I won't make him defend that even though I know that nobody is that perfect.
Thank you for your thoughts!! I really valued your input!