This is a very dear older friends story, I have her permission to share.
Her husband cheated when her children were under 5. He confessed. They had faith based counselling (both individually and together) somewhat unusual at the time but it was the one thing she insisted on. He felt like he had "lost himself" in the changes from single bloke to married dad. They rebuilt their relationship, had another child, and she trusted him again.
She loved him. He was a hands-on father in an age where that was unusual. He didn't smoke, gamble, or drink heavily. She was financially dependent on him. Separation/divorce was looked down on. She also thought that she'd not find anyone else/anyone better.
Within 5 years he did it again. He blamed stress from the death of both his parents in a short period of time. She still stayed. They did counselling again. He agreed to some changes such as moving closer to her family, no overnights apart. They rebuilt their relationship, she tried to trust him, but doubt lingered - she felt paranoid over any missing time/overtime, found herself constantly on edge looking for any signs of an affair. It would calm down for a few months then her anxiety would flair up again. She ended up on antidepressants/anxiety meds, which among other side effects, killed her sex drive and made it basically impossible for her to orgasm. She did go back to work, and she started saving - called it her car fund. She felt trapped by circumstances, that leaving would be difficult and she'd be breaking up the family.
When all their kids were teenagers, one of them was seriously ill, in and out of hospital and my friend would often be away overnight. He cheated again, and this time the other woman was pregnant and keeping it. Blamed the stress of the sick child and the lack of attention and affection from my friend. Wanted to be an involved father to the affair baby.
This time she left, using the 'car fund' savings.
And only when she and her kids were safely away, did she find out from each of the kids separately that they had been emotionally blackmailed, threatened, and otherwise used as a verbal punching bag by her ex to hide his cheating. One of her kids barely speaks to her now, and blames her for not protecting the kids by leaving the arsehole earlier. She also discovered that friends and family all knew him to have a wandering eye, and wandering hands.
She's quite outspoken that she wishes she'd left the first time it happened, or at the very least set herself up with an exit plan before the second time. Not so much for her own sake, even though her confidence and self esteem have taken quite a battering, but for her kids.
Sorry this isn't the positive story you were wanting to read.
When someone shows you who they are, believe them.
When someone shows you how little they care about you, pay attention.
What you allow will continue.
If you do stay, decide on your hard boundaries now - any of which if crossed is the end of the relationship, no if and or buts.
And sort out a serious exit plan - have money in your name he can't access, figure out what you would need to do to move out or kick him out, how much you would need in savings, which solicitor you would need, have copies or originals of important documents stored safely for you and your children.