Do glad you reached out, sometimes it's better just to write your feelings down.
I don't have kids, but have nephews a bit older than your boy. It sounds like he's probably dealing with teenage hormones and unsure how to deal with them. Don't take it to heart. Could he be missing his mates if it's just been over Christmas?
You say you can't exercise, but walking is one on the best forms of therapy. Could you manage yoga, or would the inversions bring on a nose bleed? Meditation is good, you seem silly at first, but try and get past it. Sometimes I just 'shake it off', literally, shake my arms, legs and body, usually if I can't sleep. It's a dog behaviour thing, but I think it works!
See, smell, touch and hear is useful to focus the mind. Name one thing you can see, smell, touch and hear. And deep belly breaths, humans generally breathe too shallow.
Make sure you're not clenching your teeth, I do it when I'm stressed/anxious and it makes it worse.
Could you clean the house? That helps me keep my mind occupied.