Good Morning. My Symptoms Are That During The Night I

Good morning. My symptoms are that during the night I experience movement on the back of my head/skull that reaches from ear to ear. Not the entire area at the same time but it feels like one areas bumps out and moves and then another area. If I were to liken it to something it would be like when a woman is pregnant with a baby and you can see the baby move around. Weird yes I know ... Imagine how I feel! This only seems to happen at night and I'd say during the middle of the night. It also doesn't happen every night but it seems to be happening more frequently. I can actually put my hands on the back of my head while I'm laying in bed and feel my scalp bump out. Any suggestions? Jennifer