Ok I'm really worried now please sombody help.
Well here it is basically I've been on my periods non stop for over 3 weeks.
I am not on the pill and never have been.
Ive not had sex or anything like that.

I know I should go to the docs and I will book a appointment 2moro but before I go does anyone know why my body is behaving like it is?
Is this summat I should be worried about?
Is this something I have done to cause this?
These are the answers I want and need answering:S
I'm only 16 please help.

It's nothing you did that is causing this. I'm an Acupuncture student in Florida, studying to specialize in infertility. Women's reproduction system is a very complicated one. There are a number of reasons for this. I would HIGHLY recommend seeing an Acupuncturist/Herbologist/Traditional Chinese Medicine. This is one of many health issues that we see a high success rate without surgery. Hopefully, you're in a state that it's available. The preferred education of an Acupuncture Physician is a Master's degree in Oriental/Eastern Medicine, or higher. If you have any other questions feel free to contact me.

Ok im really worried now please sombody help.
Well here it is basically ive been on my periods non stop for over 3 weeks.
I am not on the pill and never have been.
Ive not had sex or anything like that.

I know i should go 2 the docs and i will book a appointment 2moro but b4 i go does anyone know why my body is behaving like it is??
is this summat i should be worried about?
is this something i have done to cause this?
theese are the answers i want and need answering:S
im only 16 please help.

Periods can be off for a number of reasons... mainly hormonal, but there are conditions, such as uterine polyps that would also cause extended bleeding... they are most often bengin and nothing to worry about, other than of course the bother of the bleeding.
If you haven't been having periods for a number of years, it could be just part of your cycle regulating. The teen years, again due to hormone fluctuations and development, can be a time of irregular cycles.
As cybereyes2 mentioned, acupuncture can be helpful in getting cycles turned around. Many women will use it for fertility issues, mainly due to hormonal concerns.
Determining the cause in the first place will help you to know what direction to go for solving the issue.