That's a difficult one; on the one had, you have to ask yourself whether he realises how much that has hurt you, just carrying on like nothing's happened.
On the other hand, how long do you expect to try move on from it if it's hanging over you both. do you want to (or plan to) hold him over a barrell over this.
I must say I wouldn't be able to get back with a cheater because I wouldn't be able to stop 'making them pay' for the hurt they had caused, whether I wanted to or not. i would certainly feel like you if they didn't seem to be making the extra effort.
If he's gone back to 'old habits' that you're not happy with, that you were hoping would disappear, then I think you should tell him that and ask him if that's the way he's just going to be. Hopefully he'll say "no no honey" and make extra effort that won't diminish.
But if he doesn't say that, or he says he will make an effort but it doesn't last, you need to make a call as to whether you want to stay.