i did sex on 18 june 1st time in my life, my boy friend did not discharge the semen in side and i got my periods on 2 july, the 1st day of period is more pain full than i never feel before, but till now 4 august i dont have my periods, at this time i m also in vary stress due to studies and other problems, is the delay in periods is due to stress and tension, or there any chance of pregnancy? i vary worried about this please help me