Have you ever tried meditation? It would quiet down the mind and stimulate the parts of the brain that would help you to deal with the stress and difficulties of life.
I'm no expert on meditation, but I am an expert on having a mind that's all over the place, so I can definitely relate to what you're saying :-) Just try to find a quiet place and a comfortable position and "mentally step back" and just become an observer of yourself. What ever thoughts come to your mind, acknowledge them and then just let go of them. Do not start thinking about them, just observe. Notice what your senses feel and just feel them, don't think about it. Focus on what's happening inside your body, which basically means just to focus on your breathing as that's pretty much the only thing you can feel (unless you're suffering from indigestion!) Being an observer means that you don't have to live the stressful situations and chaos, but just focus on what it feels like to be human.
Becoming more mindful can also help with getting into shape, as you become more aware of what you actually need and what's just mindless activity.
I do hope you'll get it sorted. I know it's really frustrating and tiring to go through such things. Best of luck!
EDIT: When I wrote "senses feel", I was actually thinking about just the skin, but realized that of course the word "feel" might not be appropriate for the other senses :-) Anyway, the point is to acknowledge what information comes in through the senses, but not verbalize it in your mind. So if you hear a noise coming from a train in the distance, don't start thinking about "oh, I hear a train". Just acknowledge the sound and don't think about it.
Also, when observing yourself, the goal is to be objective and just acknowledge, not judge. You'll eventually notice that you'll have much more compassion towards yourself and through that towards other people as well.