what's going on please help!

Hi, I'm 17 years old and ever since I started doing gymnastics when I was about 13 I have had a very deep secret that I want to know if anyone could help. So in gymnastics, whenever I do almost any core exercise (sit ups, chin ups, climbing the rope, candlestick, etc.) I experience a sharp short orgasm. I really enjoy gymnastics but this is just getting a bit old so my questions are, is this normal? Has this ever happened to anyone before? What should I do about it? And do the other people in my class know?