My period is now 16 days late, and it is very regular...I use a menstruation tracker. I have been feeling sick to my stomach, getting headaches, severe backaches, and feeling dizzy. I did take a pregnancy test, but it was negative, so I wasn't too worried because I am on the pill (although there were probably a few times where I forgot to take it and then doubled up the next night). Suddenly today, I started getting severe sharp pains in my lower abdomen (mostly on the left side, but radiating to both sides) and severe pains in my upper abdomen, like I was going to throw up...I feel weak and started to have bright red bleeding, although it isn't heavy. all day today before the pain, I was having brown discharge that had stringy clots in it. I am debating on visiting the ER and wanted to ask your opinion.