jasmin10: You need to tell your mother so she can get you in to see a doctor. It's not normal. You could be losing too much blood and end up passing out or become anemic. YOu need to get checked out to make sure nothing else is going on inside of you that could be causing more problems - you could have cysts or endometriosis. Get checked.
This happened to me once and it turned out to be stress related, but I recommend seeing a doctor because there are other things it could be that are more serious, like ovarian cysts, although those are usually benign. Get yourself to the doctor as soon as possible.