Ataxia means "lack of order". Medically, it's used to describe a lack of coordination of gross voluntary motor control (big movements that you tell your brain to do, such as walking or writing). It can be caused by a number of lesions (damaged areas) at a number of locations. Here's some different types of ataxia and some tests you can do to guess which one you have:
-cerebellar ataxia: if you have trouble standing with your feet together with your eyes open, and have a wide stance when walking
-sensory ataxia: if you have trouble standing with your feet close together and your eyes closed, or trouble walking in the dark
-vestibular ataxia: if you feel dizzy, and nauseous, and feel off-balance
There can be many causes for damages to all of these different brain and nerve centres, from traumatic injury, to drugs, to inherited disease, to a simple vitamin deficiency (are you getting enough milk and meat?), and the list goes on.
It's hard to pinpoint a cause without doing lots of exams, which I'm sure your doctor will do. Cerebral Palsy usually shows up at around 3 years of age, and doesn't get worse over time, so it's likely not that.
Diseases that cause ataxia are rare and usually hereditary, meaning that you inherit it from someone in your family. If one of your family members has a problem with movement co-ordination, make sure your doc investigates that disease. Alcoholism can also cause ataxia.
With proper exams, your doc should be able to diagnose and treat the source of your ataxia (in most cases). Try not to worry!