Over effective senna pills?

I had a stomach bug so I took a 50mg senna pill to get it out. I took it around 10 oclock two nights ago and had a normal bowel movement the next morning and felt fine no stomach cramps anymore. Then after that for the rest of the day I had completely liquid bowel movements (4 of them). I thought that was just the pill getting out of my body. But it has continued to today and I still have yet to have a bowel movement. I knew senna was a laxative but should they be this effective?