this unstable and miserable environment will be what shapes your child's future.
What ARE you going to say when your child looks into your eyes and asks why life has to be this hard? why do they have to accept their P shagging anything that moves and they have to put up with it?
My dad left my mum (for OW) when she was early 40s. she lived alone for a while, travelled and did what she wanted to do, and then met the man she has been with for the greater part of 20 years. They are 6 years married.
So why would you not deserve a decent life? why are you a write off already?
Answer is that you DO deserve a life, you are NOT a write off, only all this OW mess, your DP treating you like this has you THINKING you are worthless.
You are not worthless. Far from it.
BUT - if there are no consequences to his betrayal of you, then where is the incentive to treat you with respect, to end his cheating, to live honourably?
In order to win back your life, your respect and your position, you have to be brave, you have to stand up and you have to TELL him to end it or YOU will end YOUR RELATIONSHIP.
He is not going to take you seriously for anything less.
This is actually a WIN/WIN situation. If you end it and he mends his ways and comes back, treats you with respect, kindness and eats shit apologises for -ever-- a while, YOU WIN.
IF he chooses to continue with the betrayal, fuck around with both of you and treat you both like fools, and doesn't come back, you will be free to enjoy a proper life with a decent man.
This dickhead needs telling to zip up his trousers, get himself down the STD clinic for a full once over, grovel like mad to you and behave. OR LEAVE. And remind him that the sooner he leaves the sooner you can get a decent man, so not to fuck around wasting your time wondering which scenario it's going to be.