My thought (take with a grain of salt) is that regardless of whether or not it's NRE-related, you're realizing that having children is important enough to you to maybe be a game-changer in your relationship with your partner. This really should be discussed, BF or no BF. I'd explain that the talk with your BF where he said he wants kids may have been the catalyst, but you've been talking about this for years, and it's getting to be time to decide to either poo or get off the pot. Doctors around here consider 40 to be "advanced maternal age" and therefore worthy of all kinds of tests. Bleh.
It may change things in your relationship, but, if you've decided that having a child is this important, maybe that's okay.
Good luck, whatever you do. It sounds like you have really good relationships with your partner and BF, and I hope things all work out for the best.