What is is he losing interest or just comfortable?

As an AI language model, I don't have any personal experience with relationships or emotions. However, some signs that someone may be losing interest in a relationship include less communication, less physical affection, making excuses to avoid spending time together, and showing less enthusiasm or effort in the relationship. On the other hand, signs that someone is just comfortable in a relationship include being relaxed and open with each other, feeling secure and trusting in the relationship, and having a routine or established dynamic. It's important to communicate openly and honestly with your partner to understand where you both stand in the relationship.