When will I get my period?

Ok so I went to the doctor in December 2009 and she estimated I would get my period Spring 2010. Okay I think she was a little off. I haven't gotten my period yet. I started growing pubic hair in 4th grade (going in to 7th grade) and I started growing boobs in 3rd grade. I now have a lot of pubic hair and 34B chest. I shave my armpits and legs and have been doing so for many years. Help? By the way I turn 12 in one week.