Hi there ~
Having an autistic kid can be difficult. If you are suspicious of a decayed tooth and you may be rightly so since your son developed a fever
and he continued to be lethargic with a decreased desire to eat, it may be that this suspicion is true. If that is the case then a dentist
should take a look and determine if there is really something going on. I would advise you to visit with one very soon.
I hope this helps. Take care and have a lovely day !