There is a lot in your post (op) that I can relate to, I'll stick to forum browsing. YES! Some (most?) of my worst triggers are right here on Susan's. I avoid most threads with a quick 'mark as read', I simply cannot view them. After some time, in weak moments, I'll open some again. I want to see how some whose posts I recognize are doing. It reminds me severely why I stay out of the threads.
It's not the people and not their progress. I am happy and thrilled for each and every one. No. My issue is with myself and my own perception of self. Their recounting(s) and their photos dig deep into me to find my darkness and bring it to the front. I am not trying to alienate people here. I'd love to here from them. I just cannot read their postings most days.
When I do manage to read, I have to close the topic without replying. I cannot keep it open in front of me .. time to move on. So, I continue to avoid. It is not them, it is me. Some day, maybe, I'll be happy enough with myself to share in their joy without having my world end for a day, or 2, or 3, ...
I have a very supportive family, all of my issues are within me.