15 y/o pregnancy scare

okay so the last time i had sex was about 2 days after my period, from what i can remeber. i was slightly intoxicated at the time but i know it was relatively close to the end of my period. anyways, i had protected sex with a condom and he did not come inside me, but im 2 days late on my period and i had one insanely day of super strange cramps about a day ago, but besides that nothing out of the ordinary. thoughts? I'm fifteen and i'm not sure what to do, or even if i should worry?