Hi there Aitch,
I'll second NYC's suggestion about seeing if you can't find a FB yourself that you connect with.
Secondly, I think I'd investigate what turns him on now (because it may have changed) and analyze where I'm not meeting that spec. This isn't an easy thing because it opens us up to parts of ourself we might not want to see. But there's really no alternative if you hope to reconnect on a passionate level.
Sexual attraction is really a terribly complex thing. A lot plays into it and some of it is hard to define. But we recognize it when we see it - or don't see it. And it's especially difficult for two people who care about each other to just say "I'm not that into you sexually anymore (or right now). So we often times have to try to discover the "whys" in a round-about way. If we can discover something - we may or may not be able or willing to do anything to change it ! But at least we know and can try to work at it in some ways.
Maybe try to get him more comfortable with telling you some VERY detailed info about his sex with others. Clues can come out during those types of discussions. And even getting closer from those discussions can improve things. The more he truly believes you are comfortable - maybe even a little excited -about his sexual side, the more you might find yourselves coming together.
But still, finding someone else that's more into you is a good move. Takes the pressure off everyone.