Flat head!

My baby girl's head is flat on the right side... Somehow I didn't notice it until the pediatrician pointed it out at her 2 month appointment. Now I'm noticing that she does always turn her head to the right while in her swing or sleeping. If it doesn't resolve by her 4 month appointment, she will probably need a helmet! I have been trying to put her to sleep with her head to the left, but any other tips or advice?