Assassins Are People Too - Assassins in Love Series, #1

Marc Francis is a paid assassin. He's got a little thing for the blond guy in 39D. One day one of Marc's enemies tries to get the drop on him in the elevator and his blond crush, Dillon Carter, from 39D, sacrifices his potted plant to save him. Marc and Dillon have a strong sexual connection and as the months go by, and they steal time together, it develops into something more. But Marc doesn't really do relationships, and Dillon worries Marc will ever be able to love him back the way he needs.
Also, when you're a paid assassin, not everybody is rooting for your happy ever after.