C.O.
Hello! I am not a doctor. So it could be a couple of things...
1. sexual transmitted disease
2. ovulation cramping - not all women get it and some don't experience until after they have had a couple of kids.
3. uterine infection - like strepB - that is USUALLY presents itself when you are pregnant - however, CAN happen to women who are NOT pregnant.
4. vaginal infection.
My opinion is leaning towards #2...i hope you are able to get to the Dr tomorrow and on the path to feeling well!!!