Sure, simple.
1. He's probably full of crap.
2. He's almost certainly full of crap.
3. If he could be any less full of crap, he'd still be ten pounds of crap in a five-pound bag.
4. The only reason that one would message an ex to tell them how awesome their current/last SO was is because they're some sort of petty sadist who wants to make the person feel bad about themselves, or is so socially inept they think that the fact they've (allegedly) been in the sack with someone hotter than the person they're attacking would actually want them more based on their ability to attract someone more attractive.
I dunno about you, but when someone's trying to use me as a booty call, I want nothing more than to hear that they did someone way better than me in the meantime. That gets me as hot as a summer night in Nevada
5. One time was a kid, I was at the county fair and eating ice cream watching this bull, and it let rip right there. The pile of crap that resulted, relative to the level of truth of what this guy is saying, still doesn't broach the the magnitude of what this guy is telling you. And this pile of crap was epic, it gave me nightmares for weeks.
6. From the onset, he really thinks very highly of himself. The reality is that he probably knows that, as you said, he's in his early 40's and not the best looking dude out there and is horribly insecure about this. He can't take take the shame of not being what he'd like to be, and so he tries to make you want to come crawling back to him so he can feel like he's worth something.
7. Guaranteed, if he really did screw these girls, they're not calling him back because he's so crappy, and this (combined with #6) makes him feel really small. Five bucks says he turns on the shower, sits in the corner, and cries before he starts texting you with all his BS.
8. The reason he texted you again the next morning is because he needs to make himself feel like less of an epic failure than he knows he is, and he failed his way out of that one, too.
What a loser.