Worried about Daughter!

Brittany • 30, married, one precious daughter.
Ladies, tell me if I'm overreacting, but I'm slightly concerned about my baby she's just over 3 weeks old. She's been gaining good weight (like, really really good), so I haven't set alarms at night to feed her. She's been great about waking me up every 3-4 hours at night to eat. Last night she went over 7 freaking hours. Holy cow! I was shocked when I woke up and felt SO guilty for sleeping so long. She wasn't screaming or anything and didn't seem any more hungry than normal, but that long stretch threw me off. Anyway, that was at 3am. She ate again at 8:00 (again with the long stretch!!). She ate over 30 minutes each feeding. We went for a little car ride and she was knocked out, went about 3.5 hours between feedings so I woke her up to eat. She ate for 10 minutes and fell back asleep. I changed her diaper, undressed her, tickled her to wake her to finish eating, nothing is working. She's squirming when I bug her, but she won't wake up to finish eating. Am I being crazy, or am I right to worry? Should I just let her sleep? I want to make sure she's eating enough!! :(