What Causes Delay In Menstruation Other Than Pregnancy?

my period has been late since the last 8 years.its normally a few days or a week late,i got sexually active a year back and after sex my period always got late.i never got pregnant.
for the last few months my periods have been on time,on the 28th.but recently i was with my boyfriend and we were fooling around,we didnt not have sex.he didnt not enter me,he was just using his hands but i missed my period.what is the reason for this? does sex have anything to do with me missing my period? ive not had sex but i missed my period after it being regular for a few months so im freaking out.please help me