What Causes Pain In Lower Back And Abdomen?

Okay so my back has been having pain the lower back and last night it was also in my front side where the appendix are but now its still in my lower back I just got over a flue and I got from my roommate he is also now over the flue and he says he is peeing and poohing blood and I heard him vomit he is having the same back pains but I'm not bleeding ny urine is clean like normal. And I'm not shivering or anything and don't feel the need to vomit