I am in the process of forgiving, but I am finding no stress-relief. Does this mean that I have not forgiven?
Forgiveness is a process that takes time. I have worked with people who definitely understand the process of forgiveness, practice it daily, and yet they still can have anger for up to a year or more. Does your anger or sadness diminish even a little? Try to be aware of these even small victories. Aristotle said that practice and then more practice is necessary to grow in greater maturity in the moral virtues. I find that this is particularly true of forgiveness because it is in the context of being hurt by others. I recommend that you be gentle with yourself, patient in the process of forgiveness, and never give up on the practice of forgiving. The dividends of stress-relief usually then come. You may not be free of all anger in the coming years, but it likely will diminish to manageable levels for you.
For additional information, see The Four Phases of Forgiveness.