Plagiocephaly?

For the past couple of months I have been noticing Liam's head being pretty flat in the back. I knew this happens by them being on their back too much. We have tried as much as we could to get him on his tummy but he hates it! We still make him do it but it's so easy to turn him over when he is screaming. I asked Dr Reese about this at his 4 month check up. She said she wasn't too concerned about it and really didn't believe in the helmets...just a change in his activities.  I did some research and it does concern me. I know this is just a cosmetic thing but I don't want us to regret not doing more later down the road. So I decided I would start taking pictures and see if he gets any better over the next 2 months. I know I shouldn't google and should probably just listen to my doctor but he is my baby so it bothers me...