Cosmo by Minerva Howe

The dragon veil has recently opened, allowing dragons to pass from the human dimension into the dragonlands. They left behind Cosmo and his two brothers, Cullen and Corbin, to guard the gateway between worlds. Cosmo has never really fit into any dimension, being half dragon and half fae, so he figures it’s a pretty good life, especially since he’ll never have a mate. And then he meets Hawk.
Hawk is old. Old enough to have forgotten whole centuries. But when he wakes to find his house has moved to Cosmo’s place, he discovers a whole new interest in life. Cosmo is perfect for him, but Hawk has some convincing to do as he and Cosmo try to come together and bridge the gap between human, fae, and dragon while they start a family of their own.

This is an mpreg dragon shifter romance.