Am I dreaming?

I got woken up by my housemate last night. Because I was singing. "Henrietta, are you alright?" she asked as he knocked on the door. I woke up. "Yes" I replied. "Were you asleep?" "No, I wasn't asleep." I replied. "Ok", she said and returned to her room. Actually I was asleep I thought. My last thought had been 'lalalala' in my dream. I fell asleep again. I had a bizarre recollection this morning of this funny conversation with her. So I tentatively knocked on her door asked her, was it a dream? No, she said, at 3am it was real :-)