I was 15 years old when my 18 year old sister picked the lock of the bathroom door while I was in the shower. When I turned around she was sitting with her girl friend looking at me standing there stark naked. She had removed the towel from the hook,told me our Mom had popped into the neighbour's and sat there with her girl friend looking at my dick, It was embarrassing because I was stuck in there not knowkng what to and sufferd the humiliation of getting a hard on. It just creeped up on me and couldn't top myself from getting a full erection. I remember feeling so much shame I never said aything to my Mom. To top it all I had a terrible crush on my sister's friend because she was the cutetest girl in the neighbourhood.