Marriages can continue after affairs, so it's not a given that couples split, regardless of how long the affair was.
I knew a couple (parents of a friend) where the man had an affair for over 20 years. He didn't leave for years and years because his wife was in ill health and he clearly felt some responsibility for her and towards his kids.
Without being in someones marriage, it's impossible to understand it.
OP- none of us can know exactly what your marriage has been like.
You could decide it's well and truly over. Not sure if you have tried counselling either as a couple or for you, yourself.
If not, maybe it's worth a shot?
If you are sneaking about, recording your H' s phone calls, it shows that the communication between you is less than honest.
Is that the basis for saving your marriage? Are you staying because you love him, or you can't imagine a life on your own?
It will help you both to decide if your marriage is worth saving. If not, you will feel in a stronger position to leave and go it alone.
Please don't stay in it just out of fear, or