Why The Menstrual Periods Are Delayed?

i had sex 10 days before my period date..i had un protected sex bt my partner had ejaculated inside bt not completely and not deep inside i had washed soon after we were done, and now i am 5 days late for my periods,my friend said that sometimes because of sex the periods get delayed, is there any chance that i might have conceived? if yes is there a way to get my periods without taking medications??