A healthy 7 week old baby will usually go through between 10 to 12 diapers per day.
You should check a 7 week old babies diaper every 1 hour to 1 hour and 30 minutes and if the baby is wet or poopy then they will usually cry and let you know they need changed.
When my kids were 7 weeks old I changed them every 1 hour to 1 hour and 30 minutes depending on how often they peed or pooped.
A 7 week old baby will usually pee around 20 times per day and there's no need to change the diaper every time they pee because that would get expensive.
Diapers are very absorbent and sometimes you can go as long as 2 or 3 hours without needing to change your babies diaper depending on how often they wet.
As long as the 7 week old baby is going through 8 to 12 diapers per day then they are likely okay but any less than 8 diapers per day then they could be dehydrated or constipated.