What Does Pink Vaginal Discharge Indicate?

My husband and I are trying to conceive. I ovulated on feb. 14. On February 22, after using the bathroom, I wiped and noticed some light pink mucousy discharge. My cycles lengths are about 31-32 days so my period should not be coming for at least another week and this has never happened before. After that time, it has not happened again. I've also been having lower left back pain. Any idea what this could be?