common name for this is mittelschmerz,can be very painful. Its also possible you released more than one egg this month.ive experienced this before but that was when i was on clomid.over stimulated my ovaries.so as a guess i think more eggies released.if this is first time its happened,wouldnt worry to much,but if happens again,I would get checked out just to be sure.
thanks very much tarajanes i think AF is deffo on the way though got back ache and my breasts are slightly tender normal symptoms for when AF is due