The title says it all:)

My son was 7lb 8oz and 20 1/4inch long and is wearing NB sizes (he's 13 days old) but they are fitting him juuuust exactly...(not tight, not loose) at birth they were pretty big on him but as of yesterday he was 7lbs 13oz, so they aren't big anymore.
I ask because he only has a few NB outfits and I'm wondering if I should buy more...but ive decided that I don't want to buy more if he is going to be done with them in less than a month.

Please include length and weight:)
Eta: for reference: he fits NB size diapers but also fits size 1 diapers