I got super tired and fatigued and thought it was me getting older but then i went to the doctor and had low iron and vitamin d. I'm still worse than i was but it's not anywhere near as bad. I also upped my depression meds along with treating the deficiencies.
I'd recommend checking your levels if you haven't already. I might just be projecting my own situation on you, though. It turned out to be worth a trip to a doctor in my case.