Hello @jenatsky.
Thank you for reply.
I'm still not 100% convinced it's not due to low testosterone, but I'm always open to find out what's wrong.

It's not CO, as I live in an area with very low pollution, very clean air and good ventilation in my home. I work as a Personal Trainer (part time) and do a lot of outdoor training with my clients.

I have been to a psychotherapist, and from her diagnosis, there's nothing wrong expect the symptoms of depression, anxiety and irritability there's nothing else mentally wrong.

I've had full blood work tests, and all the results say I'm in perfect health, aside from a little low on vitamin D, which is normal here in the north due to little sun. Everything else is almost damn in the middle of the accepted range.

I'm very active, training 4 days a week for about 3 hours and I have a pretty healthy diet. Been into strength sports since I was 14 🙂

No illegal P.E.D's. I'm to scared, as there is history of heart issues on my mothers side, so I'm not willing to take a chance that I could provoke something there.
100% natural (Aside from surgery to fix broken bones and torn muscles)

One of the biggest reasons I suspect low testosterone is that so many of the symptoms match, and when looking at the results of the test, I'm just above the minimum level.

As someone that (also) has an automotive engineering degree, my thought is "Just because it's within spec, does not mean it's optimal".
But hell, there must be something wrong to explain what's wrong right? 🙂

Still don't know what's wrong, but I'll keep trying to find out, even though I do feel that it's affecting my mental health not knowing why my body feels like it's shutting down. And in just 2 or 3 years.