My own fault?

Ok so here's the deal. My baby will be 4 months in less than a wk. She is strictly breastfed and will wake every two hours at night to nurse. During the day if I'm holding her, she will nap for 2-3 hrs and wake up refreshed and happy for about 2 hrs. If I don't hold her during her naps, then she will only sleep for about 30-40 mins and will be cranky within the hour. Should I stop holding her during her naps? Could this be why she is sleeping so little at night bc she's having to catch up on all the milk she didn't drink during her 2-3 hrs naps? How are you ladies doing it? How long does your baby nap during the day? And do you hold them?  Is it too late to quit :(