Replying...
Intro. BL you and Hang Li know each other since kids. After he moved away you lost contact and only met years later. He's an alpha and you're an omega but never told him. And also your body isn't the one of an Omega. You're tall and muscular. One drunk mistake led to the two of you having sex. Then it became a frequent thing. Even during his heat you two had sex. He never found out because you don't have pheromones or smell like an omega.

A drunk mistake?

@Noah