Nobody here can diagnose you, but from what you describe it sounds like depression. I'm assuming you talk more at other times, specifically stabler times? What makes you wonder if it is psychosis? If it was catatonic mutism, I highly doubt you'd be asking this or even posting here, let alone saying "Good morning" or "Good night".

Now if what you said was inappropriate to the situation, maybe psychosis or trauma/brain damage could be possible causes. For example:

Someone: "What's wrong?"

You: "Good morning"

Someone: "Why did you say Good morning?"

You: "Good night"

Someone: "Are you joking with me?"

You: "I love you"

OR,

Someone: "Good morning"

You: "Good morning"

Someone: Tea with sugar"

You: "Tea with sugar. Tea with sugar."

Someone: "I am a big purple gnat"

You: " I am a big purple gnat. Tea with sugar. Good morning."

It's best that you ask any questions about diagnoses to your psychiatrist.

Hope you feel better soon!