Rock n play may have caused flat head!

My 7 week old JUST finished a growth spert. I noticed his head is more flat in the back!!!?? I thought I was diligent about not allowing my baby to have a flat head from excessive laying. 
I DID NOT even think of how sleeping in this could cause him to get a flattened head! 
I soo wish I NEVER put him in it to sleep at night 😔😔😣 yes I buckle him in. I didn't for the pic.