What Causes A Short Menstrual Period And Stomach Pain While Bending Forward?

i prefer a gynacologist

i am a 17 yrs old girl.my boy friend just rubbed his penis over mine (just once). it was on 17 april and i got my periods on 8th may ie,the next month. on the same day i got exhausted(eyes go blind n go uncoscious 4 a while). n it never hapnd in my life. n the period ends in 2 1/2dayz.usually i got 2 have my periods just 3 or more dayz but tht day just 2 1/2 day.but my due date was correct.and on 18 june my belle button is paining while i bend backward or forward. i am not sure but will it be pregnancy symptoms? please help me.