Little Doctor, Big Daddy by Alex Blaine

Helping people live comfortably is a great career, but not the kind of responsibility Caleb wants at home. He needs someone who can take care of him when he’s most vulnerable, and a new patient might be just who he needs…
Dr. Caleb Billings is an endocrinologist who helps people with various hormonal conditions on a daily basis. Some are serious and some are merely inconvenient. But all of them are important to his patients, so they’re important to him. But when he’s at home and not responsible for anyone’s health and wellness, he has an unusual way to relieve stress. As a Little who engages in age play from time to time, he needs to fully surrender to that part of himself, letting go of all his stress and responsibilities to truly relax.
Mack Porter visits Dr. Billings with a situation he can no longer keep to himself. He’s managed to hide his lactation disorder for his whole life, but now, the condition that was the result of unethical experimentation when he was a child has started to affect his life in significant ways.
He can’t be the dominant lover he wants to be while constantly worrying about what his partners will think of his leakage.
Dr. Billings is an expert in these matters and the only person who can truly help him.