I hope you get through your working day well enough. You post's made me very sad for you. 
It hurts writing this to another woman but you need telling that you are not a blow up doll!
I'm older than you and pre women having marital rights. I've been in your position, ending up dealing with wretched infections and having to be restitched twice post one birth as a result.
Even in my era where becoming a lone parent was to be avoided at all cost, his refusal to treat me as more than the 'thing to service his needs' raised some eyebrows at clinic.
Regardless of taking whatever he wanted, whenever, and whatever the cost, ex DH's 'needs' swiftly turned to additional women, women without repeat stitch damage, women without stretchmarks, younger women, girls, etc, and of course he left anyway, because it was always about his 'needs', his wants, his desires, what he deserved.
It just took longer and left more damage.
I learnt anecdotally from other women that the kind of men who treat their wife as a blow up doll never then stay because they have enough access. (Being 'allowed' to have extra sex elsewhere becomes the next ultimatum once they get caught.)
Please know this, my generation all learnt it, and your generation really doesn't need to reinvent this wheel.
You're almost certainly headed for pretty much the same place I ended up in, but having been coerced up to the point he goes and you become a lone parent anyway, so he's 'done nothing wrong,' you've just 'not been enough' to keep him. You're being played.
In a way I'm glad I had no choices, it would have been even worse to live with being coerced and still then discarded.
Please talk to women's aid about how he's playing you.
I'm so sorry you're being treated like this. No matter how you may currently feel and even if you never feel it yourself, you really are worth more than this and a normal man wanting a "loving relationship" wouldn't be doing this to his FT working, mother of his 3 yr old, 20 week pregnant wife, he really wouldn't.