I Have IBS And I Know How My Stomach Acts

I have IBS and I know how my stomach acts now that I'm on medication for it pretty well...But I know I've been under an SEVERE amount of stress lately and it's been flaring up a bit, but, today I've been having VERY sudden and some what more painful bowel movements than normal and now I noticed white, coarse sand looking material in my last stool. It was a loose stool and it consisted mostly of this material it seemed. What is it? And Should I be worried and get to my doctor ASAP?