I feel like my daughter isn't growing!

So daughter will be 7 weeks in a couple days, but she is still so tiny she is just now starting to fit into newborn clothes properly.  0-3 months? Forget it, she's swimming in them. Same for diapers...still can't fit in size one. She wasn't super tiny when born she was 6.14 lbs and 19 1/2 inches, I feel like she's way smaller than other babies her age now. Does anyone else have a baby that's staying tiny? Or is there something I should be concerned about?