You ask if you'll ever get over it.
FUCK. YES.
You'll feel like you won't, that's natural, but trust me the relief you'll feel when you come out of the shitty bit will be amazing.
Like a PP said, he cheated on his pregnant partner. At the time he should feel most protective of you and excited about your shared future, he did something he knew would devastate you if he found out.
He chose a shag(s) over a family. Think how low he is for that.
If it was me, as painful as it would be, I'd leave him now to get my head around being a single parent before little one arrives.
If you stay together until they are here, you'll get into routines with baby that involve him and it'll feel even harder to leave.
I'm so sorry love but he has broken the foundations of your relationship at a critical time and the fact you're the one trying to fix it is so awful.
I've been there, I cringe too thinking back on the negging I've done to partners who have cheated on me, even hit me. Therapy and time mean that I now have excellent boundaries and am in a happy relationship.
Take control and set your soon to be here little one an example of being a strong person with self worth and the courage of your convictions.
You can coparent without all the angst of wondering if he's cheating on you again / using up precious energy on trying to "keep" him when your resources need to be focused on your little ones arrival and especially first few months which we all know are so intense anyway. But they'll be filled with joy because you can concentrate on your beautiful baby and not this wanker,
You'll be so proud of yourself for it eventually 