New poster here, I think I've read most of the thread over the time it's been up.
OP, if you are concerned that he is possibly still in love with the ex, there's something else you should consider, too (not that you need any more weighing on you at this point, but it's valid).
Sometimes, people aren't still 'in love with' someone anymore, but that past person did sort of 'ruin them' for some aspects of future relationships. I will tell you the story of my friend Bob. Bob was with a gal we'll call Janice for 10 years. They never got married, but had houses, vehicles and pets together, and were, by all accounts, pretty happy until they got engaged 6 years into it, and that was the beginning of the end. Bob was very excited to propose, planned a big, elaborate thing, bought a beautiful ring, etc. Janice accepted, but right from the start, was saying things like she wanted a long engagement. Basically, she freaked out and started looking for a way out. After a couple years of things progressively getting worse (she started not coming home at nights, going out and partying with her girlfriends and not coming home a couple of nights a week, etc.) Bob finally called her on it. Janice admitted to her that marriage seemed like a death, something you 'had' to do when you too old to do anything else. Obviously, they split up.
Fast-forward to now. Bob has a great girlfriend, Larla, that he's been with for 5 years. They got together less than a year after his split with Janice, and while they had some rocky times and split up twice in the early days of dating, they have now been living together for a couple of years. They are happy, he treats her VERY well, as well as or better than he treated Janice but Larla wants to get married, and he just keeps dodging it.
I am one of Bob's best friends, and I do truly believe he's in love with Larla, and would not take Janice back even if she tried. That said, he was SO hurt by the way things went down re: her and the engagement/imminent marriage that it has just sort of soured him on the whole concept, for lack of a better word. It sucks, because Larla's paying the price for what Janice did, but on the other hand, Larla wouldn't have Bob at all if Janice hadn't done what she'd done.
You know your boyfriend better than a bunch of strangers on an internet forum (though it can be good to get an impartial opinion). Is it possible that while he's no longer in love with his ex, their relationship shaped him in some ways that are now affecting yours?