I can echo the advice regarding Vitamin D and this is the right time of the year to test. Some people have more trouble processing Vitamin D than others so you could be taking a small amount to supplement and it still not be enough.
Are you sleeping properly? Are you getting restive, therapeutic sleep or are you suddenly waking yourself up with a snort? The fatigue for sleep deprivation can be overwhelming.
How does a 'lived experience' differ from an 'experience'?
Acute anxiety after death of my husband