Please give me advice

Danae

So i took a take action pill which is a plan b my period is currently 20 days late , yesterday i had light cramping and my lower back hurts a lil bit but my period still not here , and i dont know if it is period symptoms or pregnancy symptoms .. my breast was sore a week ago but no other change than that . the last time i took a pregnancy test was on september 8 and it was negative