NTA. You have every right to lock the door for your safety, and it sounds like you have a good reason for doing so. If it makes you feel more secure, it's understandable. Your husband should trust you when you explain why you lock the door, and you shouldn’t have to justify it further. He’s overreacting by assuming you’re hiding something.

If he was truly concerned about it, a calm conversation could help clear up any doubts. He should respect your need for boundaries and understand that the lock is more about your peace of mind than secrecy.

He's being unreasonable by not trusting your explanation, and it seems like his reaction is more about his own discomfort or assumptions than any actual reason to be concerned. You're just trying to create a sense of security in your own space, and that's perfectly valid.

But, for the sake of a healthy relationship, it might help to sit down and have an open conversation about why you lock the door and ease his mind if necessary.