Baby clothes

So ftm here and don't really know what to expect for how many of each size to get. So far I've gotten most of her clothes as gifts and haven't needed to buy any. But now that I've washed and organized all her stuff I realize I have no 0-3 month clothes. Tons of newborn, tons of 3 month. Is there a difference between 0-3 and 3 month?

Also, I'm pretty sure she will be on the smaller size because the whole time she's been measuring exact each week, but in the last month or so my fundal height has been 2cm off each week. So I'm sure that will affect how long she will be in each size.