i can appreciate and empathize with your concerns since different conditions/disorders can have similar symptoms. Your thoughts do seem quite anxious. "Evaluating" is something I do when I'm anxious. Also, i get phrases or a word stuck in my head when I'm very anxious. It's like a distraction, or something to hold onto when I'm so unsure of other things.

To help anxiety, I made a rule for myself to keep from getting too overwhelmed. The rule is I can't do two negative/harmful things at once. For example, if I'm having anxious symptoms (heartbeat fast, pacing, worrying, fearful, etc), then I cannot try to "figure things out" at the same time. One at a time only for me! If I'm anxious, I concentrate on lessening/relieving those symptoms only.

What helps my anxiety is breathing, saying pleasant things to myself about myself, getting some sun or wind or water, reminding myself of my other rules (discard unhelpful thoughts to allow helpful thoughts to step forward), listening to music, taking a walk, taking a rest, watching something, etc.

maybe you were already feeling anxious when you heard that song you loved, and it gave you happiness and relief? Maybe your mind wanted to hold onto that relief, but then it frightened you? Perhaps with practice, your mind can hold onto relief in a less anxious pattern? Anxiety is fast and hammering, for me. Slowing down to realize I have time and space helps. Telling myself I don't have to have it all figured out right now helps. Solve it later. When anxiety isn't present, I realize there may be nothing to figure out after all.

Anyhow, hopefully I was of some help, and didn't add to your worries. I offer my thoughts with care and kindness only.