I am going crazy, 13 year old and sickness

[TinCat]

We had a very similar experience last year in a younger child (10)

Had COVID then spent all winter getting sick with respiratory thing after respiratory thing. 

Would get sick, need steroids, improve, go back to school and get sick again. It went on for months until she caught COVID a second time.

Then we started having the same issues with the sore tummy an intolerance to dairy foods, and reflux. 

Eventually a paediatric gastroenterologist basically said it was related to the original infection which can change the make up of the gut, and not a genuine lactose intolerance  as they're rare to develop at this age. 

The only real healing solution was limiting dairy and time. 

That's probably not much help but you're not alone.