Did you have regular periods before your baby. I agree with the above though you definitly should have had one by now, especially if your not breastfeeding. I gave birth in September, breast fed for 2 months and then had my period by December.
I think you are long overdue for a trip to your gynecologist. If you are not breastfeeding and have not breastfed at all for several months you should have had your cycle back by now. There are any number of reasons why you have not had one but you will need to see your doctor to find out.