{{{{{{{{CJT}}}}}}}}
{{person's name}} are hugs. I've seen them used elsewhere, especially on Open University forums, but never here. Maybe I'm not looking in the right place.
You've nothing to apologise for. Don't do that, this is your thread.
Don't feel guilty about your feelings, they're absolutely valid. It's too much stress that makes me cry; afterwards I feel better able to cope with whatever it was that made me cry in the first place. Sometimes I think that there are people much worse off than me, of course there are, but that doesn't mean that my own needs aren't important and I need to take care of myself. And you need, and are entitled, to take care of yourself and your needs.
Volunteer dog walking for a rescue sounds like a good idea; is there a local rescue you could talk to about it? Swimming is a great suggestion; I used to go regularly but have had to give it up because of back injury. It would release endorphins in your brain that work to help lift your spirits. I loved that feeling of being supported by the water and forgetting the constant ache in my joints for a while.
Have you thought about getting a cat? There are a huge number of rescue cats needing homes. Would DS like a cat? You have to be patient with an adult rescue cat and get to know them but they make great companions once you do. It's a magic feeling the first time you narrow your eyes and give your cat a slow blink, and s/he does the same back at you. I'm a mad cat lady, can't you tell! My mad cat is a stroppy black rescue and I love him to bits. Photo attached. I woke him up for his breakfast too early, he went back to sleep. There's a teenage boy inside that black coat. 
A touchy subject now, are you interested in politics, in particular, how do you feel about Brexit? This organisation, DiEM25 is just over two years old now and is spreading across Europe. It's still very young and like all organisations of this type, it needs volunteers. I do what I can to help my nearest branch and it's far more energising than any Labour Party branch I've come across. Progress is another active organisation, although I think I've probably moved too far leftwards for them. If I'm on the wrong track with this, please ignore.
I hope you have a better day tomorrow.