Newborn sleeping through the night?

When can I stop waking up my new born to feed? Right now I have to physically wake her up every three hours to feed her. Can I wait longer? Maybe four hours instead? Can I let her sleep through the night or wake her up once? I don’t mind waking up at all I just feel bad waking her. She’ll be 3 weeks on Monday and is drinking three ounces per feeding

Thank you in advance!