I would never trust a guy who spoke terribly about his ex, just because, that will probably happen to you if you break up.

It's kind of confusing me too but echoing others, it just sounds like this guy is too complicated and 1 week in there is already so much drama? It really doesn't bode well for the future. The fact he has two children from two other women (?) sounds like he sleeps around a lot and takes little responsibility/does not commit. You're only 20, do you really want this? Plus, didn't he say he only chose you because the other woman was too old, but if she was a better age he would have been with her? That is something I could never stand for, to be made to feel like I was a back up option and that they would have preferred someone else.

But you know, I've been in a similar situation (without all the cheating and lying, red flags and indicating he was settling though), where things didn't look great from the outset but I stuck it out for a long time because I was too attached, I really liked him, and plus, I was scared of being alone. I understand if you end up staying with him. Just… be careful and don't put too much of your heart on the line until it's clear that there are no other women and he will devote himself to you.