I Am 19 Old Boy.8 Months Back I Was Operated

i am 19 old boy.8 months back i was operated as Testicular cancer after Chemo and Radiation i am perfectly ok. Till today our family physician don't allow me to wear any under pant and allow me to go out of home. She also advice sleep naked, It is really embarrassing me to sleep naked in front of mom and dad or 2 Sisters. Last night i got huge sperm fall at night in bed, when it was noticed by mom and dad took my to our Family physician. Dr examine and ask me to masturbate in front of her. i was very shy to do that. But absence of myself Dr advice my mom and dad to masturbate myself. My mom and dad is very clear and nice to me, they ask me to do. but when i refused it they force me to it in front of them every night. I know this is bad how can i tell my mom and dad ? Please advice