Your not going to your father’s graveside does not necessarily indicate that you have not forgiven. Forgiveness does not necessarily mean that you are finished with all negative emotions. Classical conditioning may be happening here in that you associate the grave with the incest and it makes you uncomfortable or anxious. Staying away under this condition is understandable. If you are doing no harm to your father in that you are not talking negatively about him to family members or others, you may be on the path to forgiving.
For additional information, see Learning to Forgive Others.