Advice

Hi I'm 17, I don't want to be annoying or anything but I'm really worried. I'm currently 4 days late for my period, which is very unusual for me. I'm gassy, I'm cramping, I have to pee constantly, my back hurts, and I have heartburn. If I had gotten pregnant it would have been 12 days ago today. I took a test and it was negative. Did I take it too soon? Should I trust the test? Should I retest, if I should how long should I wait?