Period did not start on "suggested" day

Hey there. New to this, don't really understand all of the acronyms, but I'll give it my best. I am TTC, my period didn't start on the day it was suggested on my calendar. My husband and I did have sex all of the "higher probability" days and then some 😉. Ha. Anyway, should I be running to the store to get a pregnancy test?!? This will be my first child and I'm really excited/nervous/anxious, basically all of those symptoms you check daily!