Leaving SO

How did you know it was time to leave your husband/SO?
We're there children involved? If so, how did it affect your children?
I'm going through so much right now. My SO of 7 years completely ignores me, never helps with chores even though I work more than him, he's cheated on me in the past(multiple times), hides/locks his phone and is on it nonstop, and recently I saw he's talking to the girl he cheated on me with a while back with brought on the feelings on hate and resentment towards him and I can't get over it this time. We also have a two year old who I don't want in any way living in a split household. :( I feel 100% bad if I did that to him. :(