Side effects of oxycodone include tiredness,
sweating, nausea, flu-like symptoms, as well as many others.
Oxycodone can also cause insufficiency of the Hypothalamus and Pituitary Gland, which could explain the fluctuating testosterone levels.
You might want to talk to your doctor to see if there are other meds you can take that might have less severe side effects, or possibly lowering the dosage.