Flat head treatments

My daughter is 2 months old and the pediatrician noticed that the left side of her head is flat. We will reevaluate at the 4 month check up, and I will be promoting her to turn her head to the other side while she sleeps and try to stretch her neck muscles as the pediatrician showed me. Does anyone know if helmets are covered by insurance? I am waiting to hear back from them, so I'm just looking for a general idea on here. Which treatments worked for your baby if he or she has this same issue?