What Causes Sleep Apnea In Spite Of Taking Trazadone?

I am 88 years old female. I have underactive thyroid for which I take Levothroxine 0.075 mg each morning. I am unable to sleep, have been prescribed Trazadone, but still cannot stay asleep. Average about 3 to 4 hours of sleep a night, if that. Would a different sleep med be more helpful to me?
Question - Besides the TSH test what would the Free T3 and Free T4 blood test tell the doctor?
I need help.
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