I can't remember when I didn't have that feeling. Mine is definitely anxiety. Once, during an EMDR session, my T asked me to envision what it looked like, and the first image that popped into my mind was a black rotten walnut with an evil face.

After that, one day my T shows up for my session and gives me a black rotten walnut she found. I carry it with me everywhere I go and look forward to the day when I can let go of it and smash it with a hammer. My hope is that when I do that, it means I don't need to feel that way anymore.