Has anyone ever had back labor?? Can u describe what it feels like!?

I got my cervix checked Wednesday and then when I got home I passed quite a bit of blood but I figured it was my bloody show or just irritated cervix. I didnt bleed at all thursday but Then woke up around 2am this morning and passed ALOT of blood again (bright red) and the clinic wants to see me at 8am but now I think I'm having back contractions but I'm not sure??