12 days old baby constipated?

Karen

First time mum here and need help. Please mommas my baby is only 12 days old and I have been feeding her breastmilk only although with the bottle (she was born at 35 weeks via CS and we have not had any success with breastfeeding). She eats very well but her poop is not as loosed or watery as that of an infant should be. My mum keeps saying it is because of what I eat. What can I eat so my baby's poop isn't solid (not like adult poop though).