Baby only sleeps when held at night

I have a one week old baby girl. She is EBF on demand when showing hunger cues. I end up feeding approx every 2-3 hours (during both day and night). She currently will only sleep at night if I am holding her - meaning I don’t sleep at all at night. She is generally pretty sleepy in the day time and will nap most the day, alone in her bassinet and doesn’t need to be held.

Why does she feel the need to be held to sleep but only at nighttime and not during the day? Any recommendations on how I get her to start sleeping at night without me holding her? Please help I’m so tired.