Over 6 Hours Ago (it's Now 3:15 A.m.) I Had

Over 6 hours ago (it's now 3:15 a.m.) I had sudden severe abdominal cramping, intense sweating, followed by a few episodes of very dark almost black diarrhea. Since then the pain in the pelvic area has not subsided, though I have had no further diarrhea, no nausea and no vomiting. In fact it for the last four hours or more, when I try to defecate, nothing at all comes out. It's as though totally blocked. The pain is constant, but varies from extremely uncomfortable to acute. It reminds me a little of the pain I had from a ruptured ovarian cyst back in 1962 when I was 19. I have IBS, though for the last many years its been under control with fiber supplements. I haven't been able to sleep at all, am comfortable in no position and since there's been no change over 6 hours, I'm getting concerned it may be something that needs attention in an emergency room.