Hello. Welcome to Healthcare Magic. It s often difficult to sort out the cause of mid-cycle bleeding, as it can be triggered by any number of factors. If your last normal period started on October 8 and your cycles are around 28 days long (and if you ve had unprotected sex during your October cycle), you could have conceived around October 22 -- give or take a couple of days -- and implantation would have occurred 6 to 12 days later. So it s possible the light bleeding that started on October 28 represented implantation, and a pregnancy test should now be positive -- if you are, indeed, pregnant. (Pregnancy tests typically don t turn positive until a day or two after implantation.) If your pregnancy tests have all been negative, you have to consider other causes for your mid-cycle bleeding, such as an ovarian cyst, endometriosis, stress, thyroid disease, obesity or a pelvic infection. Your pelvic, vaginal and low back pain are suggestive of endometriosis, an ovarian cyst or an infection. In some cases, an ectopic (tubal) pregnancy will cause vaginal bleeding and pelvic pain without triggering a positive result on a pregnancy test. All things considered, it would be prudent to give your gynecologist a call. He/she may want to order another pregnancy test and rule out any potentially serious causes for your bleeding. Good luck!