I would recommend that you start with a complete physical examination. Tell the doctor all your symptoms so he/she can help you in the best way possible.
For my best guess: It is possible it could be coccydynia, which is really a collection of conditions with different causes and treatments. The pain can disappear spontaneously or with treatment. In some cases it can continue for years, possibly worsening. It is five times more common in women than men and it appears that in most cases the pain is caused by an unstable coccyx, which causes chronic inflammation.
Hormonal variations can also affect this condition and your varying menstrual pattern might also be consistent with this. Blood would not necessarily be associated however, so we may be off base here. I think it's worth investigating the possibility. An orthopedic specialist would be the one to consult for this condition.
Good luck with this.
The answers in online forums are for information only and are not intended to substitute for medical advice and care. Please see your personal health care provider for further evaluation of your individual case.
Debbie Miller, RN