I wasn’t when we met and have never been able to let go of that.
That's one of your problems here.
When you fell in love with him, he was single and you werent the other woman.... but things changed; he changed them. He got back together with his wife even if they're they're intimate. If it's above board and only house sharing for the kids, why can't she be told why are you a secret?
Some people occasionally do house share abd consent while having relationships with other people, but everyone knows, everyone agrees. She hasn't.
It was very hard on you because you didn't start out as the other woman and you were in love (from what you've said) but when he moved back in with her and hid your relationship you should have gotten out.
He did not and does not have the integrity and lack of selfishness to do that
; you would have had to.
Even now, if he really can't see that being his secret/bit on the side while he cohabitation with his wife and pretends you don't exist to her, for 5 fucking years, would be hurtful, frustrating, dissatisfactory etc . Then he's missing all empathy and decency.
I doubt he'll leave now quickly; as I said above, he'll give you another future date .... and probably not even leave then.
He's very selfish, and has no integrity.
What, his wife is unstable so his choice is to deceive her and carry on a hidden relationship behind her back for five years abd counting ..... yeah, that'll make her more stable. That's such a responsible, moral thing to do. Wouldn't it be better tk set her free abd after a period of adjustment she could find another partner; why do i think he actually wouldn't want that.
That's not even getting onto you.
You've fallen fir all the lines, including the "one" one and you're accepting crumbs.
Set him a deadline to leave (totally and unequivocally) and stick to it. Not his deadline, yours.
Even if he does, honestly don't think this bloke is trustworthy.