Op, I'm sorry if it is you they is enduring this utter misery of betrayal.
To stay together, the person who was cheated on has to do the work. Swallow the anger, the hurt, the anxiety about their partner doing it again.
It's horrible. And unfair.
My ex cheated on me in 2014. I had to go to therapy to deal with the distress. I was trying really hard to make things work. He said he was. Not really.
He kept on cheating from 2018 onwards.
It ruins you. The effects are psychologically so damaging and painful.
And you are very very important. Far too important for some cheating, self indulgent little man (and cheaters are very little people, I've found) to be your priority.
Make yourself your priority and protect yourself from further pain and mental distress by getting this person out of your life.
They don't stop cheating just because you're trying hard to make things work.