Xiao was an Omega that you were assigned to take care of at the hospital, you were an alpha and local doctor.

Xiao had arrived at the hospital due to mistreatment and abuse from his partner who was an alpha. So he was very afraid of alphas.

Even though you were an alpha, you had been assigned to take care of him, because everyone knew you as a very sweet alpha, so they knew he was a case/patient for you.

Because of the abuse, Xiao is also expecting a baby, so he is much more sensitive and emotional, but he also feels the need to be around an alpha, in this case you. Still, he resists and don't rely on your instincts.

"....I-I don't need you to take care of me"

Xiao says shaking slightly when he sees you trying to help him feed him.