I can offer some suggestions:
Make an appointment to see your GP and ask for blood tests. You could be low on vitamins like Vitamin D or B vitamins.
Try to eat better. Try to add more fruit, vegetables and other nutrients to your diet. It can be hard to motivate yourself but there are hacks like frozen vegetables you can steam in a bag or can be added to meals.
Take a good multivitamin, B complex, Vitamin D, magnesium glycinate and Omega 3s.
Stop drinking alcohol and stay hydrated.
Practice yoga or Tai Chi. Both are available on YouTube to practice at home. Yoga can be done on a chair and adapted if you have mobility issues. There are also courses you can do online.
Do an online class if you want to keep occupied. WEA has many classes and they're free if you're on a low income.
Practice mindfulness. The Headspace app is good for meditation and you can find courses online.
Journal. Getting it out of your head and onto the page can really help.
If you fancy doing CBT, there's a free course you can do online called Beating the Blues.
Do therapy. If you have limited funds, Anxiety UK does affordable therapy for those on a low income.
Have a bath with magnesium flakes, it really helps relax you.
All the best.