Looking for the title of a book I read where it was about a world with a "well of souls" and everyone was extremely religious as mandated by a church in order to keep from being possessed by demons that were consuming souls, making the amount of souls grow less and less. Babies that were born had to get a donor soul within minutes of birth or they died. The church turns out to actually be mostly run by demons if I remember correctly and I know that at some point the main characters sister get pregnant and they have to escape after finding out that the true purpose of the church was to farm souls for consumption.
I think this is Rachel Vincent's The Stars Never Rise series. The first book, titled The Stars Never Rise, was published in 2015, which fits your timeframe.
Sixteen-year-old Nina Kane should be worrying about her immortal soul, but she's too busy trying to actually survive. Her town's population has been decimated by soul-consuming demons, and souls are in short supply. Watching over her younger sister, Mellie, and scraping together food and money are all that matters. The two of them are a family. They gave up on their deadbeat mom a long time ago.
When Nina discovers that Mellie is keeping a secret that threatens their very existence, she'll do anything to protect her. Because in New Temperance, sins are prosecuted as crimes by the brutal Church and its army of black-robed exorcists. And Mellie's sin has put her in serious trouble.
To keep them both alive, Nina will need to trust Finn, a fugitive with deep green eyes who has already saved her life once and who might just be an exorcist. But what kind of exorcist wears a hoodie?
Wanted by the Church and hunted by dark forces, Nina knows she can't survive on her own. She needs Finn and his group of rogue friends just as much as they need her.
From this review:
Well, the future of the United States sucks. Demons decimated (and still is decimating) most of the world, we discovered that there were souls! But the souls are in limited supply. Thanks to the discovery of demons, the Church is like "HA! We told you!" and now has all the power, and as a result, we're ass-backwards into the days of the Puritans. Purity is prized, your life is controlled, you need permission to do pretty much anything, and if you're unlucky, they'll sterilize you when you're a teen if you're seen to be a potentially unfit parent. Life is really, really awful.
And it's even worse for Nina. Her mom is a deadbeat druggie, and considering there are strict laws about being a parent and being, well, an employed parent, Nina and her sister Melanie are fucked if the Church discovers them. Nina struggles a lot, food is hard to get, bills are difficult to pay, and sometimes she has to resort to selling herself to make ends meet.
This review specifically mentions they call it a "well of souls":
One of the truly interesting aspects of the book is the world-building. The idea that somewhere exists a well of souls which can run dry, as it actually happened in the book, is fascinating and wonderful. On the other hand, I feel that Vincent's description (be it direct or indirect) of the reality Nina lives in is a little too vague, even superficial at times.
Found with a search for
"well of souls" church demons