Need to find out "what's wrong"

For almost 2 years now, I have had this problem where, no matter what I do, I can't seem to stop thinking about, analyzing, and researching what's wrong with me. It is genuinely getting in the way of me completing everyday activities and hitting deadlines (e.g. I'm doing my work and I can't stop thinking about it even with effort; it's kind of like an itch that doesn't usually go away until you scratch it). I will have the same conversations over and over, re-analyzing the same situations and ultimately not making much progress, especially since I'm not a professional, so I can't conclude anything definitive.

Has anyone experienced this or anything like it, or have an idea of what this could be caused by? Also, does anyone have any strategies to deal with it? Thanks so much.