I Am A 45 Yr Old Female.for The Last 2

i am a 45 yr old female.for the last 2 months while I am on my menstral period I have severe pain in my lower back.also near the end of my cycle I notice that there is a brownish red color to the blood being discharged.pain gets severe enough that at times it hurts to walk.different types of cancer runs in my family.any ideas of possible problems that I may need to discuss with family doctor?