We as BS's take a huge hit to our self esteem. IT HURTS, and we do feel that we aren't enough, but that's before you fully grasp the situation, and the reality of their choices.
His choice to act out has ZERO to do with you, and 120% to do with his broken self. You need to learn this, accept this, and remind yourself daily of it.
He used to whinge he didn't get enough. Since dday, I have given him more sex to see if it helps and he still almost strayed.
Obviously I'm not enough for him and it has completely broken me. I don't feel like the same confident woman I used to be and now I'm worried that this will turn him off me more
This makes me so sad for you. You are acting from a place of fear. You fear that if you don't give him what he wants enough he will act out again, and that will be your fault. Sex should be something you enjoy to be close and intimate with your partner, not some bargaining chip so he sticks around. You deserve so much more than he is giving you. However you are the only one, let me repeat that....
YOU ARE THE ONLY ONE THAT CAN DEMAND THE RESPECT, HONOR, AND LOVE YOU DESERVE....
Start setting some boundaries, and telling him what you are not going to tolerate, and being some fuck toy should be at the top of the list.
He needs to be groveling at your feet for what he has done, and he needs to be singing your praises everyday.....But your real self esteem has to come from within.
This goes back to what I am always saying about R. The toughest part, and the biggest part of healing is healing yourself, learning to love you for who you are, and being happy with that. Once you learn your worth and base your self esteem on that, it won't matter anymore what he thinks. He will either get that you are freaking awesome, and a goddess, or he won't and he won't deserve you. But you get to choose.
Start doing things for you.
If you like your hair done, go do it.
If you like the way having mani's make you look and feel go do it.
Go buy yourself some pretty panties for everyday, pretty ones that make you feel good, that aren't uncomfortable, and also don't look like granny britches.
Spend some time on looking yourself in the mirror each day telling yourself you are worth so much more.
Start doing things that you enjoy that make you who you are/were before all this, or even better who you want to be....
Take lessons on an instrument that you want to learn, take a dance class, anything that will make you feel even more awesome than you already are.