Hello Euripides: Since this is your first post, here on PC, welcome to PsychCentral!

Thanks for sharing your concerns.
Hopefully there will be some other members, here on PC, who will have some useful suggestions for you. What I can tell you is that I'm an old man now.

But I have spent pretty-much my whole life dealing with my own mental health issues in secret. I know, from personal experience, that it can be exhausting. Plus, just as you wrote, it wears you down. And, over time, it does indeed become increasingly difficult to keep it all under wraps, so to speak.
The thing is though, at least from my pespective, there aren't any magic answers to this... no secret remedies you just haven't heard about that will begin to make everything better once you find out about them. The answer is one of those things you've already mentioned... therapy. From my perspective, you need to find a therapist you feel comfortable with & delve into all of this in depth & over time. It can take a few tries to find the right therapist for you. Not every therapist works well with every client. But mental health therapy is, at least from my perspective, the way to go for the majority of people... & most probably for you too.
Of course that is not to say that there aren't things you can do to help yourself too.

Here are links to a bunch of articles, from PsychCentral's archives, on the subject of healing from depression:
https://psychcentral.com/disorders/depression/
https://psychcentral.com/lib/strateg...ng-depression/
https://psychcentral.com/blog/9-ways...ve-depression/
https://psychcentral.com/blog/10-thi...at-depression/
https://psychcentral.com/blog/9-step...ion-naturally/
https://blogs.psychcentral.com/mille...ery-structure/
https://blogs.psychcentral.com/mille...om-depression/
https://psychcentral.com/lib/tips-fo...ression/?all=1
https://psychcentral.com/blog/the-bi...my-depression/
https://psychcentral.com/blog/9-ways...sts_position=0
https://psychcentral.com/blog/7-more...nd-medication/
My best wishes to you...