I did both on my chest and the floor. My son was holding up.his head right away so i just supported it while we were on the floor cuz he was really bobbly!
Did you start on a floor mat or just on your chest? I have been doing some chest tummy time I guess. She really wants to lift her head but I'm scared she will lift it and then smack it down.
You can start it right away and try actually suggest it so babe canget used to it but not for long periods at a time. I did 5 mins about every hour he was awake.
My pedi told me we could start at anytime at our 2 week checkup. I do tummy time on my chest, baby girl likes that better than being on the floor.