Getting baby to nap?

Our 4.5 week old is really struggling to sleep during the day. Everything I read says she should be sleeping 15-17+ hours per day and she usually gets 10-12. She's pretty good overnight, but just won't nap enough during the day. We nurse, change her diaper, swaddle, give her a pacifier and put her in a rocking bassinet with classical baby lullaby music. And all we see are eyeballs. Any other recommendations? She usually isn't fussy, just awake.

I haven't tried putting her in a dark room yet because I'm not sure if that will confuse her sense of day/night and I don't want to lose the good sleep she's getting at night.