I Am Having Almost Like Labor Pains In My Lower

I am having almost like labor pains in my lower abdomen, there is pressure in my rectum. I am not constipated and my appendix is gone. It has woke me up in the middle of the night several times but last night it started and has hurt constantly since abuout k2 or 3 in the morning. I don't seem to be running a fever. I am stumped. I am 64 years old and my younger sister had rectal cancer 12 years ago and had radiation and chemo and has been cancer free. I had a colonoscopy almost 5 years ago and all was well. I have an appointment in 4 months for another.