Ah OP, just another data point, but want to let you know you are not alone, and there is nothing whatsoever 'wrong' with you. This can just happen, and can be difficult to parse initially, once you become conscious of it.
I think it can occur in clusters. The only real solution is to take your time and slowly unhook yourself from them.
I am about to leave an unhappy LTR, and have also had to distance my sister and closest friend. All unrelated, but similarly not good for me. I prioritised them and their feelings for many, many years, but only began to take a close look at the dynamics more recently.
My sister is my only surviving relative now, it was important to me that we had a good connection, but over the space of 5 years she wore me down with her anxiety and resting most of her problems on to me. I communicated clearly and respectfully, but no joy.
At the same time I also realised that my close friend was perpetually keeping me at arms length. I was always on the outside looking in, and came to understand that she was very controlling and did not wish me well. It was very, very difficult, initially, to accept that the three closest people to me were not my friend.
I did manage to create distance without drama and now only do birthdays and xmas. There has been no conflict, but I can definitely sense the close friend is unhappy to see that I have 'woken up', and has sent me a few rather cold and pushy emails. I have ignored them, but sent a birthday card with lots of love and best wishes. This is my preferred way to deal with it and get on with rebuilding my life.
I does and can happen in such clusters. Since we have had our confidence or our spirit worn down by a significant other (in my case my DP), it can have the effect of drawing other people towards us who feed on that energy and are attracted to our passivity and openness. Becoming more focused and self aware, I have noticed that they tend to back off, as they do not like the version of us that grows, evolves and has courage.
A restart is preferable to this perpetual self questioning which puts you in the role of a victim. I would recommend casting this off and selfishly rediscovering what YOU want from your relationships, setting fair but firm boundaries, and putting yourself into new hobbies and interests.
Oddly, once I had loosened their hold on me, my anxieties and self criticisms ceased almost over night. Sometimes what we think might be a problem with our own mind turns out to be as simple as gross incompatibility.
Narcs, energy drainers and control freaks can sniff low self confidence a mile off. Like my sister, they almost NEVER gravitate to secure, happy people. My sister collects damaged people who depend on her, from her clients in a caring career, to her remaining friends, who are fast running for the hills.