Flat head

We went for our 4 months appointment this week and the doctor said my baby has mild flat head and it should be better my his 6 month appointment. If it isnt better she said they would refer us to a helmet specialist. His head isnt horrible but its been really bothering me since i noticed around 2 months. We dont lay him on his back for long periods of time mainly just at night. During the day we do tummy time or he lays on me to sleep or we sit him in a saucer or bumbo seat. The doctor said we are doing all the right things. Has anyone been told their kid has a mild flat head? Did it fix itself or did your baby have a helmet? I am not sure what to expect but its really bothering me.