Does anyone know?

so i found out that my 5 week old is lactaose..so i stopped pumping..i was told buy a friend that i should stop pumping because that will produce more milk...since im not feeding anymore i stopped..and im in so much pain..can i hand express or should ijust let it be?? my chest is so sore and tender and very painful and very hard..ive takedn pain medicine..does anyone know if im doing the right thing?? i cant feed anymore due to his allergy..also he has colic..does anyone have any helpful things??