Why would I still feel sore when I have sex a year after having my baby?

Hormonal. Could be lots of reason for pain with intercourse a year after having a baby. If you have been breastfeeding, then hormonal causes can lead to vaginal dryness and pain. If you had a significant tear during childbearing, then that could also cause the pain. The pain could be totally unrelated to childbearing though so would recommend that you consult with your gyn.