I can’t find a thought?

I’m currently feeling sad but I’m struggling to find a thought creating that feeling. When I search for the thought things like – ‘ why am I feeling like this’ ‘it doesn’t make sense that I’m feeling sad’ ‘nothing has happened to make me feel sad’ ‘I shouldn’t be feeling sad’. But my understanding is these are all thoughts that would go in the T line if my circumstance was ‘sad’ but I can’t find a T that’s creating the feeling of sadness now? I experience this (having an F but not being able to link it to a T) often and I’d love any support on it? Also just to sense check my C in this case would be experiencing physical sensations of sadness in the body?? If not that I’m also not sure what my C line is?