had protected sex with my boyfriend, can i be pregnant?

[macchhima]

i had a protected sex with my boyfriend for the first time and that too on my period date. it's been 4 days now, but my periods haven't started yet. My menstrual cycle is not very accurate. now i want to know can i be get pregnant? when do i have to get a prega test? and if the result is positive, can i get a pill from chemist, or do i have to visit doctor for abortion? i'm very scared. please help me.