It is most likely coincidence .
Thanks for the query.
As per your clinical history it appears that you are having respiratory track infection.
Since you have taken oxycodone
5 mg before with no allergic reactions , it is most likely coincidence . But oxycodone can aggravate your dry mouth
& respiratory problem . So please consult your treating doctor to change oxycodone to some safer pain killer.
I am happy to hear that you are going to ENT tomorrow for your mouth ulcers .
If I were your treating doctor, I would advice you Plenty of fluids , antiseptic mouthwash , Vitamin C
, artificial saliva spray for symptomatic treatment & like to investigate and manage accordingly.
Hope I have answered your query. If you have any further questions I will be happy to help.