Were we separated at birth? Your journey is exactly as mine. I experienced a traumatic event when I was 9 years old and have suffered from low-level depression since then with periods of major depressive disorder. I am also now a senior and I'm experiencing the same feelings as you: not looking forward to anything; feeling blah; crying a lot; having anxiety; and the unrelenting fatigue. I wasn't diagnosed until I was forty. I've been on medication since then, but after a while it didn't work anymore and I had to change meds. Recently a psychiatrist gave me samples of a medication to supplement my regular antidepressants. It is named Vraylar and it worked beautifully; I hadn't felt this good in years. However, my insurance would only pay for it for six months. The cost out of my pocket would have been $1300/month after that 6 month period. Now I'm back to where I started. And talk therapy doesn't help at all. This is a brain condition and no amount of talk therapy will change that. It's biological, folks.
You didn't mention what medication you've taken.