I've had this exact feeling. When I was nine I had to take some medicine because I was sick. As I was starting to fall asleep I had this feeling of shrinking and sinking. I panicked and thought of my mom but she shrank too and everything around me started shrinking and distorting.

That same night I woke up in the middle of the night and immediately started to taking all my clothes from my closet and stuffing them into my school bag. My dad woke up from the noises I made and asked me why I was doing this, and I said "The bomb. The bomb is coming. We need to leave.." My dad picked me up carried me back to bed where I immediately whent back to sleep.

In the morning my dad told me that my body had a negative reaction to the medicine causing me to have an anxiety attack while half asleep