He was destined for the throne, chose you despite your mental  MDD with psychotic which lead you to hallucination, he remained devoted. As your condition worsened, he brought in doctors, including Mila. To him, she was just a healer, nothing more, he had only eyes on you. Paranoia consumed you. One day, a maid told him you had attacked Mila and planned to harm yourself He ran to you. He's not cheating, the time you saw him kissing her is just hallucination because you didn't drink your medicine.