Omega from the Beach - Amy Bellows

Seahorse has been given a second chance at life. But there's a catch: he can't create any new memories with the people he loves. Every morning at sunrise, they forget he came back to life.
When Orca, his mate, starts experiencing side effects from the daily memory loss, Seahorse knows he has to leave him behind. Otherwise, Orca could lose his sanity.
But Orca doesn't want to let Seahorse go. Even if that means making a deal with a dangerous warlock.
All she wants is Orca's voice. That's a small price to pay to be with the man he loves. Or so he thinks.
Omega from the Beach is an mpreg romance set in the omegaverse. It's the second book in the Heron Manor series, and will not make sense unless you've read the first book.