I have a 2+ week-old newborn and if she's awake, she's sucking - usually on me, but her hands, her own arms, husband's chest, if we go to kiss her she'll suck on our noses... I had an oversupply with DS and am pretty positive I do/will with this one as well, and a very forceful letdown, so sometimes she'll cry even when she's on the boob... She's gained A LOT (I'm talking 4 oz+ a day, no exaggeration - she's up almost 2 lbs from her 5 day checkup, and she was almost 8 lbs to begin with), and while I'm not at all worried about the weight gain or anything, I wonder if she wouldn't be happier just having the pacifier occasionally. DH gave it to her when she was crying in the car 2 days ago, and she was happy as a clam, happier than when she's on my ever-spurting boobs... I try to feed her every time she roots, but that's turning out to be pretty much every 45 minutes... I honestly hate the paci as it makes me feel like I'm somehow not doing my job, but if lets her nap and gives my breasts a little break, I'll use it. OTOH, if she really does need to be eating every time she roots, I'll keep putting her on there, only sometimes she clearly does not want the food (pushing me away and crying, and then sucks on her hands...)
Nursing constantly - always hungry or can I give her the pacifier?
I say if you don't have any latching issues and this has been her pattern for a while, go ahead and use the paci when you need to and don't feel guilty about it. Some babies have a high need to suck and a pacifier is a good solution to meet that need (especially in the car!). Be aware that there is a 2-3 week growth spurt so if this is new, I would wait a few more days to make sure she is not trying to increase your milk. It sounds like you are doing a great job and she is getting enough milk!