If he was as serious and as much in love as you say and committed about you, he’d not be secretly interacting with women and lie about it (which indicates ulterior motives on his part). He’d not act like a player. He’d act like a man who is seriously into you
When a man is as into a woman and is as serious like wanting to marry no way no how he’d do things this guy does.
He said things he thought you wanted to hear. That’s what guys like him do. They think if they tell you all this lovey stuff, you’ll fall for it. It doesn’t work this way. When you meet a man who really is serious about you, none of this stuff you described would be happening. He isn’t interested in exclusivity or commitment. Or things would be entirely different.
Yes there could be white lies in a relationship, like when I sometimes complain that I gained weight my husband telling me I look just as gorgeous as the day we’ve met. Well he might think so but logically speaking I can’t be possibly looking exactly like I was as I am aging. But if he secretly talked to women and lied to me, it wouldn’t be while lie. It’s just a lie.
I honestly recommend therapy to get to the bottom of your attraction to players and even wanting to go back to a player who is already known to be dishonest. Good therapy could help to sort sources of that attraction. So you don’t fall for it again. Good luck