Time doesn't do the healing, what it does is gives you space to go through the grieving process and come to terms with your loss. This is no quick fix solution, people find different ways of coping and take different lengths of time to work out their own coping mechanism.
My advice is to take time, use time but don't expect time to heal you. Remember your dad, keep the happy times fresh by talking about them and looking at photographs. Don't dwell on what you can no longer have, rather remember the pleasure and happiness that he gave you and remember that is what made you what you are.