11 year old boy obsessed with his health

Hello: my 11 yr old son has been on vyvanse 40mg for 4 years.. everything was o.k (School, appetite, sleeping ETC.This summer we have been giving him weekend medication holidays. Everything seemed to be going fine but now he is obsessed with his health( Weight, asking about different diseases,asking to take his temperature every 10 mins, asking to take him to the doctor when nothing is wrong.then he will snap out of it… Has anyone else experienced this type of behavior.He takes his vyvanse dailyr during summer camp and his counselor says he is fine.. this just started recently. I am wondering if it is the 2 days a week with no vyvanse that could be causing this….. I will be sure to mention this to his DR. THANK YOU RONNIE P.S it happened today for the first time. when it happened he was on vyvanse and he took it Monday and Tuesday.