Low Baby Weight

Posting anonymously but has anyone experienced giving birth to a low weight baby? My unborn little one was just seen via ultrasound today, was supposed to be the last scan for my whole pregnancy, at 37 weeks, but just found out that his size is just 32-33 weeks. Not sure what happened cos his past scans were normal, all accurate for his age. I'm kinda getting depressed cos I thought we could give birth soon as I'm feeling contractions already but now we went home with the bad news trying to delay the birth. Any insights? ?