How can I keep going like this

Back story:

I'm a middle-aged woman. After the Covid lock down, I went on a two year journey where I lost 140lbs (half my body weight). Towards the end of those two years, I was working out 6 days a week and only eating 1400-1600 calories a day because I was still technically overweight. At some point, I stopped losing weight even though I had a calorie deficit most days.

I started feeling drop-dead exhausted, even though I was getting 8+ hours of sleep a night. While I had never really ENJOYED working out, I was able to get an energy boost and sense of accomplishment out of it. That stopped being true and after awhile I could no longer justify forcing myself through my workouts. So I stopped, and went to the doctor to try to figure out what was happening.

I spoke with a nutritionist, who said I was eating enough and the right types of food. A sleep doctor found nothing. My primary care doctor ran every blood test under the sun. Cardiologist ran a stress test. Everything came back normal. Cardiologist had the audacity to tell me all I needed to do was keep working out, which, my dude, you're telling me the solution to not being able to work out anymore is to work out???

So after about a year of looking for explanations I kind of gave up. Went from working out six days a week, to four, to three. Now I'm lucky if I get two days a week. I still eat mostly unprocessed foods, smaller portions, although my snacking is up a bit, and I've gained back about 80lbs in three years. I don't drink caffeine after lunch and have a regular sleep schedule. Still drop dead exhausted pretty much 100% of the time I'm awake.

"Depression" was also a suggestion from the oh so helpful Cardiologist, and look. When I was 15, I was diagnosed with OCD/anxiety/depression, and I've been through a couple of depressive episodes in my life, so I know what those feel like. I was not depressed then. I certainly am now, due to the way I've been feeling physically for the past three+ years (and because my dad died in December after a brief put traumatizing health decline).

And lately, I'm wondering just how the hell I'm going to keep doing this for the rest of my damn life. I'm single, working full time, and about 20 years away from being able to retire. The only things keeping me going at this point is feeling responsible for my three cats and not wanting to lose my house.

Most days when I get home from work I can barely make it up the stairs to my bed before crashing for a couple of hours before it's time to feed myself and my cats.

I used to read, I used to play video games, I used to watch TV shows with lots of twists and turns and try to figure out the surprises ahead of time. I don't really do any of that any more, except for a little bit on the weekends. I just don't have the focus.

So if anyone is still reading (unlikely) how the hell do you do it. How do you continue to exist and function while feeling like shit without going absolutely bonkers. Does it ever get better, even for a little bit?

I want to be clear I'm not thinking of hurting myself or anyone else, just feeling angry and helpless and tired of having to just focus on getting from one moment to the next.