Hi My Name Is Alexis And I'm 13. I Don't

Hi my name is Alexis and I'm 13. I don't know why but I'm peeing blood. It doesn't hurt or anything but every time I urinate there's blood in the toilet. I also think I've been sort of moody lately (but I don't know if that's a symptom). The blood doesn't only come out when I pee though. When I go to change my clothes it soaks through my panties and I don't understand because there's no pain at all. Do you have any idea what's wrong?