Depression, anxiety, feelings of inadequacy

Hi again to all. Have posted on other threads but there doesn't seem to be anything specific to people with ongoing mental health probs. I was reassured by some other postings on other (some related) topics by some really lovely Gransnet members, but am again really struggling with feeling inadequate, inferior and low.
Each time a family member or friend tells me about their social calendar or social life,or what their adult children are doing, I mentally compare my own life to theirs and dread other people telling me about (for instance) dinner parties they've had, parties they're invited to etc. I get a sense of relief when someone says they aren't doing much over Christmas and New Year. I have to add that as I've said previously I KNOW I have much to be thankful for - supportive and long-suffering OH, a home, loving and independent daughters, some family still living, a few friends we see now and then, etc - it's just that my wayward brain automatically compares me and my life to that of others, whether friends or family, and I am so ashamed and disgusted with myself for not feeling I can share in the happiness or good news they tell me about. I hide it very well, make the right noises, etc, but inside I feel anxious, deflated, inadequate and inferior - and I know it makes no logical sense at all. Why should it matter if Friend A or Family Member B has had friends to dinner or has been invited out? It doesn't affect me -and yet it feels as if it DOES - it makes me feel either left out or inadequate for not having such a hugely active social life. I imagine that the lives of others must be infinitely superior to mine (and yet logically I know that isn't so).
I then ruminate, brood, feel miserable and fail to appreciate what I DO have. I don't WANT to be like this. I am prey to other anxiety along the way too. I am angry with myself - I know it's not a good way to live. Short of a bullet to the brain or a frontal lobotomy (both rather messy) I don't know of ways to cope with this. I do struggle with anxiety and depression anyway and these repetitive, negative thought patterns are probably a part of that. I've struggled for years to combat them, to no avail. I feel I am the only person feeling like this and that makes me feel even worse. I don't expect any magic wands - at this stage of my life, the wands are rather worn out and battered - but I am grateful for the space to vent, express how I feel without being judged, and maybe there is someone else on Gransnet who might feel similarly (though I guess it's doubtful as I feel such a monster for having these thoughts and feelings at all).