Hi Stillhoping. I am no expert, still trying to work out my little one.
But I think the main point is - every baby is different. It took me a long time to recover from the birth. The only way I survived those early weeks is because I asked DP to do the night feeds so I could sleep. I just couldn't stand to hear her cry so I never tested the theory that crying tires them out.
Poppy did eventually begin sleeping less during the day and longer during the night. Now she sleeps from about 9pm to 6am without a feed, and often goes back to sleep again until 9am. So there's hope!
I don't think there's any harm in the baby sleeping in the day, it's just the mum who needs the night sleeps. So do whatever you can to get through these early weeks. Things will change.