Write a story about my older sister discovering my tiny penis was a premature ejaculator. She would lift her shirt and flash her huge boobs, causing me to instantly explode in my pants, she thought it was funny. She would drop her towel after a shower, letting me see her amazing naked body and of course, fill my pants with cum. One day while walking to my room in a towel, she dropped to her knees, pulled back my towel and kissed my penis making me over her cleavage and face in my cum.