First he began going out more frequently, working 'late' and making an extra effort with his appearance. 
Then he disengaged from you emotionally. 
When you asked him about this, he called you stupid....
After a few more weeks, you tell him you are unhappy and don't feel loved.............and he fucks off, as fast as he could, without so much as a backward glance ??!! 
Honestly ? He's definitely been cheating (or trying very hard to !!).
He only felt 'guilty' when he had to face you ffs ! (And the 'guilt' only lasted as long as he could actually see you ffs !)
He's a selfish bastard who actively went looking for someone to cheat on you with. He's never going to be the 'man' you hoped he was.
Look after your baby and yourself.
Leave him to do whatever it is he's been doing for weeks/months now. He showed you no love or respect when you were sat at home with his baby growing inside you, and now it's your turn to ignore him, because he deserves zero love/trust/consideration from you after what he's done.
And quite honestly, I'd be choosing a new birthing partner who actually cares about you, because he'll make the birth all about him and his wants/needs/hunger/tiredness etc
After the baby is born, you'll need to make some hard decisions about whether or not he should even be put on the birth certificate (because it will give him the 'right' to oppose your parenting choices in the future).