sick toddler

Ju
I feel like the mother of a newborn all over again. My son has a double ear infection and a lung infection called RSV. Normally, in a toddler RSV isn't considered extremely dangerous, but he has asthma... He has been coughing so much it's terrifying. I put him down for bed and 20 minutes later he's up screaming. I rush into his room and he's coughing and crying so hard he's gagging like he's going to throw up and he can't catch his breath between coughs. I get him to calm down, nurse a little, and eventually rock him back to sleep. 
Now I'm laying in bed, unable to sleep. What if it happens again? What if I don't hear it over the monitor? What if he wakes up not coughing, but gasping for air? What if. What if. What if. I have an anxiety disorder, so I know my mind is playing tricks on me, but seriously, how am I supposed to sleep?!