Waking to feed

I’m a FTM and I have a one month old. My daughter was born 8pounds and 4 ounces and got down to 7 pounds 3 ounces but now we are close to or at 9 pounds. (We bought a scale to use at home.) I am exclusively pumping and currently feeding her 3 ounces of BM every 3 hours. Do we need to wake her at night to feed her. I feel like she’s not getting enough sleep at night because we are waking her to feed. If we can let her sleep how long can she go for without eating? I heard no longer than 4 b/c you don’t want their blood sugar level getting low. We don’t go see our pediatrician until her 2 month check up which is 4 weeks away.