This story is definitely a few years old. I believe it was Dean/Gabriel, but I could be wrong?
This was an AU society where Angels lived most humans and it was sort of normal. Angels were not super common, but were the top of the social ladder. They basically had their pick of eligible omegas. Gabriel wasn't huge on getting married but accepted an arranged marriage to a poor Omega who wanted to put his brother through college. He hoped that they could eventually care for each other, but in the instant that they got married there was Soul touching moments and he realized Dean was terrified of him. He decided to do his best to give Dean space.
Meanwhile, Dean, who has grown up basically knowing he'll be sold off to the highest bidder, is falling in love with the fun friendly guy he was forced to marry who turns out not to be a complete dick.
Dean gets pregnant and runs away for some reason that I can't remember, but I'm pretty sure it was angsty and had to do with insecurity? And Gabriel comes to find him right before the baby is born and they end up happily ever after.