Alpha in Heat by Anna Wineheart

Alpha-preg. Enemies-to-lovers. Boss/Subordinate. May/Dec.
Jesse Sinclair has secrets. A mountain of them. At twenty, newly-rescued from a human trafficking ring, he’s eager for a new beginning. That means not looking at his case files, and not knowing what his captors have done to him. It’s all in the past. It doesn’t matter anymore.

Except it does, when his PTSD gets him off on the wrong foot with his fire station deputy, Dom. Dom is alpha-as-hell, twice his age, and it’s clear he doesn’t want Jesse on the team. Jesse joins the station family anyway, and everyone welcomes him with open arms. That is, everyone but Dom, who challenges him to drinking matches.

Dom, who subdues him during his panic attacks.
Dom, who kisses him and pretends it didn’t happen.
But the biggest secret is the one even Jesse doesn’t know—back in the Facility, his body was altered. Something Jesse should’ve discovered before following Dom home one night.
The simmering heat between them explodes. Jesse ends up conceiving a child. He’s not prepared for this at all.