Baby cereal

My daughter is breastfed and since she was never getting enough thru that we started supplimenting her when she was a week old. She is almost 6 weeks old. And the past week she just doesn't seem satisfied with the breastmilk and formula and we are having to give her more formula than before or she eats way more frequent. Have any of you mom's giving your LO cereal yet? My mom said she gave it to me at about this time due to the same reason.