For the passed 5 days or so I've been having really bad cramping, but no period has come. I haven't had a 'period' in over a month. I had light spotting for 3 days or so last month. My period is a month late. I have been a little nauseous throughout the day yesterday and the day before. Took a pregnancy test about 1-2 weeks ago but it came out negative. Also, I'm very sexually active and use birth control. Why could I have such bad cramping, but no period?