When to start pumping?

I’m FTM and my baby is 2.5 weeks old and strictly breastfed so far and I haven’t started pumping at all because my lactation nurse at the hospital said to wait until 4 weeks for my milk supply to regulate so my body didn’t think I had twins and get too full to often.

However, I’ve heard from friends and others that they started pumping right away and stocked up a lot and others that didn’t had their supply dwindle out early. Should I be pumping already or am I ok to wait? I’ve been nervous about breastfeeding and getting it right! Do I just pump the breast she doesn’t fully eat from after a feeding or do I pump both in between feedings?

Thanks!