Why does my newborn fuss all day?

She’s 6 weeks old today. It’s been happening since 2 weeks ago.. she’ll be fed, changed, and burped and then just lay there and fuss. It’s not actually crying, it’s just yelling. She’ll yell, be quiet for about 20 seconds, starts yelling again, and the cycle continues… and it’s ALL DAY (unless she’s asleep). My first born wasn’t like this so I have no idea what to do