My baby is never hungry?!?

My baby is 6 weeks old and doesn’t seem to be hungry. I try putting her on the Brest at least every 3 hours but she would only feed for 5-10 minutes and then fall asleep or be done eating. I feel like this can’t be enough.

Doctor says she is fine, everything is normal and she is appropriate weight for her age but I’m still worried. At night she even sleeps for 6 hours without waking up.

Every week she has put on an average of 150g/week until last week when she didn’t even put on 100g. Anyone else have a baby that isn’t hungry?