Eh tu normal la at 3 weeks, formula babies memang sering minum, boleh jadi setiap 2-3 jam or even more frequent if your baby is cluster feeding, especially early on. Red face boleh jadi dari few things like heat, nappy rash spreading, or just dari crying/feeding intensity, tapi better you check with your paediatrician or midwife just to be sure especially since baby very small pa. A few of my mum friends had the same worry at 3 weeks and most time it was nothing, but better to ask your doctor to put your mind at ease.