For some it works to stick with it and get through the aftermath of the affair, for others it doesn't.
By sparing literally everyone's feeling but your own, you will not be able to get through this.
He betrayed you, your BF betrayed you, you caught him. He promised to sever all contact, he didn't. That is enough, the betrayal upon betrayal. I reckon also that this affair won't be the last, as he has managed to get away with this one.
Your 'friends' chose a pair of heinous cheats over you? they are not friends, and need to be told that. disgraceful.
If you stay in this dreadful situation as it is your DC will watch their mother fade to nothing, you could very well be on a path to depression, if you don't open up, share the burden and get some real caring support, depression would be what I predict. I've had it, nearly killed me, I would not recommend it to another living soul.
If you stay in this situation and by some miracle manage to do so with your mood manageable, your DC will still suffer as you will not be full of joy and love and happiness to share with them.
If you face up to what you can't fight, a H that tbh is NOT committed to doing literally everything in his power to win your heart, your love and your trust back, and put yourself and therefore your family first, you might be surprised that once the hurt and betrayal has loosened it's grasp of you and you are free to see yourself for the wonderful woman and mother that you are.
In time, and it won't be overnight, you have a rollercoaster of emotions to deal with yet, you will start to come out the other side and feel normal again. By hiding this, by protecting the reputation of your H and his OW, by not telling your parents for fear they may treat him as he bloody well ought to be treated, like the shit he is, you are carrying the weight of all this on your own. It's too much one person, you will buckle.
Is your DH/BF sex life really worth your life? The happiness of your DC? If you don't radically change the day to day, you are showing them how they will be living, would you wish that on them? I bet you wouldn't!
Please do one thing, please go and talk to CAB, see what help you are entitled to, what help you can expect, and how much money you can expect your H to provide you with. Sweetheart, it is far too early to think of new dad, you need to have the space to be kind to you first! 
It might be tough for a while, but freedom is pricey, look at all those people dying for it on the streets of the Middle East at the moment, you will get there in the end, and I can assure you, the momentary discomfort will be worth it.
You are being treated abysmally by everyone around you, and not allowing those that could help you to do so. This is unsustainable, it'll break you, please don't let it get to that.