No, I don't think it's ever really possible to forgive and forget.
If you think it through, it makes no sense to do that, to do that would involve simply pretending to yourself really.
The bottom line is that this tells you that the man you thought he was doesn't exist. He's a cheat, a liar, and he doesn't have your back and doesn't respect you. He's weak.
You could decide to carry on loving this man as you now know he is. But how crap would that be - to decide to throw your life away on someone you categorically can't respect, can't trust, wouldn't have chosen? That's forgiving - but not forgetting.
Or you could decide to tell yourself that this was a 'mistake'. A 'blip'. He 'didn't mean it'. This is the road he's certainly started on with the counselling, by the way - the message is, I wasn't thinking straight. It wasn't 'me'. You can try this option - the joint 'forgetting' - but it's not real. You'll know deep down, and it will torture you every day, that he knew full well what he was doing, weighed it up and decided to fuck this woman while you, his pregnant wife, knew nothing. Bleurgh.
Those are your two options.
I would tell your family and even think about moving back to have the baby. It's such a vulnerable time - you may think it would be better to stick it out until afterwards but it's SO much easier to go under your own steam and settle before you are whipped into the baby whirlwind.
Also think of someone else who could be your birth partner. I would imagine having him by your side at that most intimate time would fill you with rage and sadness- not a great mental state for birth.