Side sleeping?

So I took my 2 month old in for her Dr appointment yesterday. The doctor noticed that she tends to lay on one side of her head more often than the other, which is causing her head to be slightly disproportionate. He said he wants us to stretch her neck the other way every diaper change and he said to roll up a blanket and put it under her back to prevent her from turning to the side she prefers. My only concern is putting the rolled up blanket on her back tends to make her sleep more on her side than on her back. Should I be as worried about her as I am? I feel like I constantly have to make sure she’s ok