Still hoping for the best

After being told, that if I can't get pregnant, I should try on my period, which I listened, and I did. That day, i lost my period, and only bled when I had sex or severe pain or cramps. Now, right in my belly button, I get really bad pains, and now I get really bad cramps, my period lasted 4-5 days at that. Wondering when I should take a pregnancy test? Can't wait another 31 days because my period is always late