No bm for a week.. resorted to very small glycerin enema.worked immediately but had severe cramping. 5 hrs later & hasnt stopped, in excruciating pain?

Must see a doctor: A glycerin enema should not cause cramping. If you are in excruciating pain then you need to seek medical help. A blockage can become very serious if left untreated. Signs of a blockage after using the enema as described would be diarrhea despite still feeling backed up or when you did have the bowel movement, if it was long and thin and again you still feel backed up.