Do you use a pillow for your baby? My baby is 8 weeks old and I only use a pillow on her when she is in view. Afraid to use it at night. When can she start using pillow?

I used a dimple pillow for her even when at night since she was a newborn because we didn't want her to have a flat head. Subsequently after 4 weeks she had a lot of phlegm and preferred sleeping on her tummy and we stopped using pillow for the night.