Convinced i have lung cancer

I am a 18 year old male. Never smoked. I trained swimming from 6-14 years old. 2 years ago i had a really bad virus and since then i developed a cough. Its not as bad as when i was sick but its still there. 10 days ago i started researching about lung cancer because my shoulder blade started hurting. I went to my doctor 3 days ago and he said that my lungs sound clear. I have good saturation and spirometry. Last 10 have been hell. i am nonstop thinking about cancer. Also i started having some weird pain in my shoulders and arm and right side of my chest also hurts sometimes. Tommorow im going to do some blood and urine work. My doctor said i should not worry about cancer. Do yall think im overthinking and how do i stop it Note: I have a pretty bad posture and im currently very overweight.