My periods are always slightly irregular, so it's not unusual for me to be a week or so late. But this month I was over 2 weeks late. I was experiencing sharp pains in my lower abdomen and into my vagina. That lasted for 2 days. I had sore nipples and was feeling nauseous at night. I took a pregnancy test 1 week after my missed period and again 2 weeks after, both were negative. 2 days ago I started bleeding but it's much lighter than my usual flow, barely anything and is chunky. Should I be worried?