I am 29 years old and have been on the birth control pill for 15 years. I have not ever missed any pills and for the past few months have been in a good routine with taking them at the exact same time everyday. I was on antibiotics for 2 weeks from Nov 16-29 but took extra precaution with condoms during that time. My last period started about 2 days late on Nov 24 but was otherwise normal, perhaps a little lighter than normal. About 13 days later (Dec 7) I started spotting a pinkish-brownish discharge that was the consistency of mucous. It was only present when I wiped and lasted 7 days (ending yesterday). Today (Dec 14) I have slight lower abdominal cramps and lower back discomfort. My period is not due for another week and I never have cramping or other PMS symptoms. I do not think it is very likely that I am pregnant, but what could be causing this spotting and cramping?