Help?

So im 18 about a month ago my boyfruend and i had protected period sex (which was late night and neither of us really finished we were so tired) but im currently 6 days late for my period. Im not the most regular but its usually only a matter of 2-4 days. i know from past experience that my bf has a large amount of pre cum so im afraid of what may happen but i am unable to buy a test seeing as i come from a family that has very strict policy on sex before marriage. Whould i wait it out longer? Or what should i do? I fear destroying my entire relationship with my mother..