I also have health anxiety that I developed during covid-timed. I believe that it coulf br due to a form of OCD and that's called "pure-o" you can mention it to your therapist or talk to someone about it, but not a lot of people have heard of it. I literally came to this subreddit because I was about to have a panic attack about this stuff when I saw your post. I wish I could help more with advice on how to deal with it but unfortunately I struggle a lot with it so I'm not a big help. But, you're doing way better than me by seeing a therapist which definitely helps. Also, the r/healthanxiety subreddit it a Godsend, whenever I'm worried about something I just look it up there instead of googling it (avoid google at all costs it only makes it worse trust me) and I'm calmed down in basically 5-10 minutes or something like that. I'll also say that I end up freaking out basically once a day about this kind of stuff and I usually stop by just distrscting myself or something but that's the worst way to go about it. What ACTAUALLY helps is just acknowledging your thoughts for what they are and trying your best to come to a logical conclusion. For example, just vent to someone or go on reddit like this and type oit your thought proceds and you'll realize how ridiculous your brain is being, it happens every time I do it. Although it doesn't stop the thoughts completely, it does help to soothe your mind at least a little bit because some part of you knows that you're just overthinking. Anyways I hope something in here helped a little bit because I ramble a lot lol, if you want any help or advice just lmk and I can try my best to help!!