I am also still breastfeeding my 17 month old DD and at her 12 month check up with the CHN was told the very same thing!! I said I was giving her yoghurt and cheese and she told me she needed more calcium and that she should be drinking cups of cows milk! It's so amazing the attitude of so-called professionals towards extended breastfeeding. None of my friends are still BF and they are totally supportive but all of the baby clinics I have been to have been a lot less than helpful. I was very adamant about BF from the start (and even stayed in hospital a couple of extra days to be sure it was estalished) but it's really no wonder people who are unaware of all the benefits don't go through with it because of all the negativity.
Jennifer, you are doing a wonderful thing for your child and should be very proud!