Does Having Sex For First Time Delay Periods?

i'm 15 years old and i usually have an irregular period , one month i get it and the next month i don't then the month after that i get it again. i was taking birth control to regulate it but my mom made me stop because it was making me throw up too much. i stopped it about a month or two ago and got my period when i usually get it a month after missing one.i had protected sex about to weeks and i've been hearing that if you're having sex for the first time it can cause your period to be delayed . i didn't get my period last month which in my mind i think i was suppose to get it this month i'm about 5 days late i'm worried i might be somehow pregnant do i have anything to worry about?