My mom left me over night with some of her friends when I was 8 years old. I cried myself to sleep. It wasn't until later in life I realized she could have been possibly cheating on my dad.
Oh my gosh, that's such a heavy thing to think about. Did you ask her or confront her?
Yes, but she denies it. 
Well, I hope they've figured it out together during this time. 
They stayed together 39 years and then my dad passed.