Hello, Thanks for posting, It would have be more informative if you indicated the date of your LMP or if the bleeding occurred away from the day of your expected menses. Usually abnormal per vaginal bleeding signify there is on under going uterine abnormally and at times due to drug especially hormones or birth control pills. But since you did not mention pills, then it is better we think of other causes. Given the presentation of the bleeding it will be wise to rule out pregnancy ( though with the complete absence of associated abdominal pain makes it unlikely) by doing a pregnancy test and possibly visit a gynobs for pelvic ultrasound. Ectopic pregnancy can present as per described. Then also likely are pelvic infections (though unlikely because of absence of signs of infection and abdominal pain). All other uterine causes of bleeding such as hyperplasia, PCODs, fibroids etc need to be ruled out by a gynobs. Excedrin do not have as side effects bleeding per vaginal but rather black, bloody, or tarry stools; coughing up blood or vomit that looks like coffee grounds. If that is the case (and I did not quite understand the site of your bleeding but assumed it was vaginal bleeding per your presentation) then I suggest you stop taking the medication and call your doctor. Hope this helps