1) There's a biological component where happiness follows a U curve. Mid 40's tends to bottom out on happiness then steadily increases. Useful to know since riding it out is a viable strategy. 
2) This translation  of Marcus Aurelius's Meditations is powerful as a daily reminder that no matter the year or station in life, the struggles are universal. Focusing on what's in your control and "knowing thyself" goes a long way towards fighting overwhelm.
3) Modern hypnotherapy is worth studying and possibly doing a session or two with a skilled practitioner. It's basically a shortcut for hacking into your subconscious and un-sticking negative loops without needing to spend years in therapy talking about the past. It's gained popularity in high performance communities, CEOs, athletes, etc. But important to know the more modern version is different than hypnotherapy from 10+ years ago. It's also not stage hypnotherapy. Much more like lucid dreaming where you're still completely aware. I particularly like Marisa Peer's Rapid Transformational Therapy. Her books  are worth reading. I can connect you with RTT practitioners or coaches if you're interested. I've worked with a few.
 (random link, but useful article) https://www.amazon.com/Meditations-New-Translation-Marcus-Au...
That’s the Hays translation. I have that one and the language is much better than some others I’ve seen posted.
Of course. It’s the Gregory Hays translation, as mentioned in other comments.
This one is my copy.
Idk your country, but incase it is US I included this link too.
Reading this book was a miracle cure for my anxiety, it literally vanished overnight from previously extreme levels. It is 2000 years old, the works of Marcus Aurelius, the Roman Emperor. It is very logical in its approach to handling highly stressful situations. I don't know how a female will respond to it, but its worth a shot.
Its now 5 years later, and this problem has remained solved for me.
Keep lifting and eating more. I don't generally give out diet/fitness advice since the entire industry is so full of shit, but to become successful you really have to experiment and try things out for yourself. I was a hardgainer for a long time, I started out at 6'0 140 lbs and years later got up to 220lb after a lot of trial and error.
Make sure you get 8-9 hours of sleep a night. Sleep deprivation lowers your T levels quite substantially.
Take cold showers to help with mental toughness and willpower.
Quit watching porn and cut down on fapping (once a week is a good amount I think, but the less you can the better)
Take zinc, it's one of the only supplements that have actually been shown to increase T levels in healthy men. Ashwagandha may also help, data is inconclusive on effects of T levels in healthy men, but it does reduce cortisol quite a lot which can help.
As far as emotions go...there's nothing wrong with a man having emotions but I do think that the way they handle their emotions matters a lot. Men should really only be using their closest male friends to confide their problems, insecurities, etc. I usually only tell my problems to 1 or 2 people at a time and sometimes I don't even tell anyone. I find that journaling and plans of action help a lot with solving problems as well.
Lastly I'd strongly recommend reading Meditations by Marcus Aurelius, which is more or less about stoicism. Must-read book for any man.
Edit: more details
For that book, I read a couple every day. I read them on the way out the door in the morning to help me stay grounded. 'The obstacle is the way' is another really good stoicism book, that one is easy to read straight through'.
Meditations is a good meatier book: https://www.amazon.com/Meditations-New-Translation-Marcus-Aurelius/dp/0812968255
You're doing great.
I myself prefer the Gregory Hays edition after seeing it recommended elsewhere.
I also just enjoy typesetting stuff! (Figures, since I am a graphic design major.)
Project Gutenberg has been a great resource, lots and lots of examples/books that require different styles of organization. I am currently working on a LaTeX version of Beowulf, the fun part of this for me has been trying to create a page layout that does the poem justice and treats all the footnotes and sidenotes nicely. I've also made my own copies of Tom Sawyer and Huck Finn in similar fashion.
Another thing I am working on is Marcus Aurelius' meditations. I bought a copy of Gregory Hays Translation, which I used as an exercise in creating a "journal" format in LaTeX. Now, I am playing around with showing several translations of Meditations (a number are on the internet) and putting them in LaTeX so that the same passages, but translated into English differently, are side-by-sde.
I have a number of these little projects. Only a few of them have been finished.
How to Be A Stoic by Massimo Pigliucci is my favorite, and the first book I read on it.
The Guide To The Good Life by William Irvine is also pretty good.
Ryan Holiday's books are good too; I just finished Ego is The Enemy, and while not strictly Stoic, it has Stoic values. He also has a daily devotion type book called The Daily Stoic.
You can also get this version of Meditations. I haven't finished it, but I think it's safe to recommend Meditations without having read it entirely.
The main key to Stoicism is to learn the basic ideas, and just be deliberate and conscious in life with the ideas; it's hard to change how you view things and react to events. You have to be conscious of it. A good amount of introspection helps a lot too. You can catch yourself doing something and correct yourself instead of letting your emotions and impressions lead you. Try to reflect every day on what you did a good job of and what you did a poor job of; thinking about these things makes it more likely that you'll do better the next day
This might help you with that.
I recommend reading "meditations" by marcus aurelius
*There are many translations of this book and the one I feel is easy to read is the one by Gregory Hays: https://www.amazon.com/Meditations-New-Translation-Marcus-Au...
MOTD #13: "We all love ourselves more than other people, but care more about their opinion than our own."
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If you don’t have it I would highly recommend you get one; the Gregory Hays translation of Meditations. Amazon Link
Want to read more books on Stoicism? checkout these lists: r/Stoicism’s the Stoic Reading List | Ryan Holliday’s Lists 1 & 2| Goodreads
As always if you have a favorite part of Meditations or want to see any other stoic passage in a future posts, please feel free to message me or comment anytime. Anyways, have a nice day/night where every you happen to be… All the best, Chris.
MOTD #9: The three things you need at this very moment.
MOTD #2: "If you’d only let go of the past, entrust the future to Providence, and guide the present toward reverence and justice."