that usually happens if you've been eating a lot of fast food or unhealthy food. There's an Oprah about poop thats actually kinda interesting that you can prolly youtube!
You're 'poop' changes depending on what you've been eating, it could just be a case you had eaten different foods to normal or not taken in as much, or too much from it than you usually do. It should settle but if it doesn't see you're doctor :]