Obsessing over my health

Good evening everyone I am sorry for the long paragraph but this is my first time on here: I am a 21yo male who has had pretty good health throughout his whole life (no serious issues whatsoever) but I have always had really high anxiety levels (especially in regards of health and illnesses) and a tendency to overthinking, I have never received a formal diagnosis but looking at my past I worry I might suffer from some sort of ocd. Exactly a month ago what started as a itch on my thigh became a rash and then my corresponding lymph nodes started to hurt, now after a month and a half completed antibiotic treatment (I know I should have went all the way but I felt better and stopped taking them, silly me) the rash is still there (even though it reduced significantly) but my lymph nodes are still kind of hurting. I got my blood tested and my doctor did not find anything wrong with me but my brain immediately put me in front of the worst case scenario and, after a couple of google searches, I am now almost panicking because I am scared my body developed some sort of incurable illness. I booked another check up and after a ultrasound exam the doctor did not find anything to be worried about but my brain is still stuck on the worst case scenario and has been obsessing over it for weeks now. I got back into my old habit of having to recite certain prayers a certain number of times before going to bed in order to avoid having a panic attack and this worry has became a constant situation for me these days. I have no idea how to convince myself that I am fine and I probably just got an infection that is causing the swelling, but please anyone I would love some feedback, as crazy as I might sound right now I have been living in a state of fear and I am extremely worried.

Anyone please, I've been obsessing over this for weeks now I have no idea what to do to stop being terrified

I just hang in there until it burns itself out- I mean, if the doctor hasn't found anything...