I'm very worried and anxious about the cyst in my child, he is five months…

I'm very worried and anxious about the cyst in my child, he is five months old now. We have had two ultrasounds and they say everything is normal, almost all babies have them like this. It will go away by the age of one. Have you ever seen anything similar? How did it happen? He's restless during the day and barely sleeps. It feels like his sleep is getting shorter and shorter.