The halachic status of cervical bleeding depends on where in the cervix it originates. Bleeding from a wound or trauma to the external part of the cervix does not render a woman niddah. However, the bleeding you experienced seems to be from endometrial tissue that remains attached to the cervix where the uterus was formerly was connected. Even though you no longer have a uterus, this is halachically considered uterine tissue. Thus, the bleeding is considered uterine and can render you niddah.
If you experienced an actual flow of blood, comparable to a light period, then you are niddah. You need to count the five minimum days, perform a hefsek taharah, count seven clean days, and immerse in the mikveh. You should continue to keep all onot (yom hachodesh, the haflagah, and onah beinonit). Please read our article on veset haguf to determine whether you have established a veset haguf from your headaches and whether you need to separate then as well. Once you cease to experience menstrual-like bleeding, you can get back to us for further guidance.
If your bleeding was lighter, your status depends on the laws of stains. Please review our articles on stains and toilet paper, and get back to us with any further questions.
If you are not niddah, or after you have gone to mikveh, we strongly suggest taking precautions, such as wearing colored underwear and not looking at toilet paper, to avoid becoming niddah from any staining.
We wish you a refuah shleimah.