You say the long distance isn't a problem; you have plans to be together again.
Big fights (when you don't even live together to annoy each other) would seem to be a problem, though. Here's what's a red flag to me: Intentionally telling you things to upset you.
I don't know how much of a threat the ex is to your relationship, or the other women he mentions. It's not the women: it's that he knows this is an issue for you *and brings it up.* My man friend is civil and cordial with his ex-wife: they had two children together. He dated - a lot- after his divorce. He's friendly with some of them, too. I don't care.
But the late husband: he was a piece of work, sometimes. One day he told me that a woman flirted with him and made a pass at him in the grocery store. We both laughed about it. A few weeks later, he brought it up again, out of nowhere. He told me the story several times over the next few months, and the whole thing started to strike me as manipulative. One day, he said it again. I was quiet for a minute. Then, I slowly, calmly said, "You keep telling me the same story about that woman, over and over. If that woman is more important to you than I am, you're free to go." He never, ever brought it up again.
When boyfriends act like yours, I wonder if they're trying to end the relationship by manipulating the partner into breaking up. That way, he feels relatively guilt free ("I was only being honest with her") and additionally, play the sympathy card ("My girlfriend dumped me") with any new prospects. Or it could be that he's just terribly immature, and getting you riled up over other women strokes his ego. Either one is a good reason to move on, in my opinion.