increased sleeping today

My baby girl is 6 and a half weeks. We have a pretty good routine each day and she is usually awake throughout most of the day but today she has been mostly asleep and will go right back to sleep if I wake her up. No signs of illness. Any idea what's going on?! I'm afraid I won't be getting any sleep tonight and we have to be up at 5am to head to a specialist appointment for out of town. Maybe I should have been sleeping with her!! Ha