Why is this thought (surgery) preventing me from doing my daily things?

I'm not sure if me having bad anxiety have something to do with this but this thought interferes with my daily stuff, like watching anime, learning a language, and drawing... this thought gets in the way and it's like "don't draw or stuff, instead, let me think about this thought or a catheter or something similar" this thought has been the most in my mind for some time now.. it bothers my days and everything.. even if I watch or draw or stuff, after I will still think about the thought, I want to get rid of it..
Why is this thought (surgery) preventing me from doing my daily things?
Post Opinion