Finding thoughts

Hi… Need help on how to find thoughts causing a feeling. I’ve been feeling anxious severals days in a week for the past few weeks. So i wanted to find the thoughts causing this feeling of anxiety. However, when i start to pause to watch what im thinking my thoughts seems to elude me. I ask myself what am i thinking right now that is causing me anxiety but after a minute of trying to watch my brain i came up with nothing. But what i notice when i pause is that i tend to focus on the feeling and how it feels on my body. And when i do that the feeling gradually fades so then finding the thoughts seems to be harder.

I noticed this also when im doing thought downloads. Where if im doing something like preparing for work or walking or watching there are a lot of thoughts running in my mind. But when i get to write them down i can only write a few.

Is there something i can do better?