What Causes Chronic Lower Abdominal Pain With Constipation?

For the past several days I have been experiencing intermittent pain in my extreme lower abdomen mostly in the center of my lower trunk area. It started with constipation for a couple days which is very unusual for me. After a couple days I was able to have bowel movements but it id not seem to totally empty I m colon. I no longer have that sensation of bowel fullness but I still get the pain. I have also been experiencing chills and fatigue since Sunday. I usually wake up after tow or three hours in bed no longer cold but rather drenched in sweat, I am a almost 68 years old, female. I had a colonoscopy with some polops removed about 3 months ago. My bowel habits are ordinarily very predictable and unimpressive. Any suggestions?