Sleep help

Please don't shoot me... but I'm having the opposite problem from my 4 week old little girl. She's wanting to sleep 6+ hours at night. She's exclusively breastfed so this isn't good for my supply nor her weight gain. She's still having plenty of wet and dirty diapers, but she's trying to sleep through the night already and I don't think she's ready for it. I'm going to set alarms so I wake her up to eat after 4 hours but I'm still worried. Does anyone have experience with this?