Moonlight Without Dawn

Looking for a story where an obsessive male lead wants to keep the heroine by having a child with her, while she already loves him. The male lead is so unhinged that he takes her to see his secret, but she keeps throwing up. Thinking she can’t accept all of him, he locks her up. Only when the nanny realizes the heroine might be pregnant does he nervously take her to get checked. Once he learns she’s pregnant, he wants to use the baby to keep her by his side. Extremely obsessive.