I'm sorry for the pain you're experiencing right now. Family of origin issues are the most difficult to deal with, because they take us right back to all those emotions which we couldn't yet understand or deal with when we were small, and yet are agonizing to have to wade through now in order to live them, own them, and ultimately discard them.
I just want to assure you that it is definitely worth reexamining the past, because it allows you to have a future free of all the unfair miseries which were visited on you as a child. I've related this before, but I was molested as a child by my parents' best friend, a man who was like another father to me (at least that's what everyone thought...). Really looking at that relationship and its results took me years before I was ready to face it. However, having got to the other side of forgiving this man, means I'm actually fine with the fact that all these things happened to me.
For years, I was angry that he effectively isolated me from the rest of my family (who only have good memories of him), that he made it difficult for me to trust others, have a "normal" sex life, etc, etc. I didn't think I'd ever be able to forgive him, because he has never apologized or shown remorse. Besides, he didn't deserve it!
The process of forgiveness taught me that forgiveness actually has NOTHING to do with the perpetrator of the hurt. Sure, you learn to show them some compassion for their incapacity to be the sort of parent you required. Other than that, it's about acknowledging the false beliefs about yourself and the world which the abuse created in you, and choosing to affirm what's best and strongest about you--what allowed you to survive and rise beyond what you experienced.
I know exactly what you mean about thoughts of the abuse leading to sinking feelings, but post forgiveness it's just impossible to feel that any more. Also, the kind of forgiveness demanded of you as a child was false because it was forced, whereas the kind you choose for yourself is an act of self-affirmation.
That said, forgiveness is absolutely your choice to make, and can only be done on your timeline. It took me 20 years to get there. However, if you ever reach a point where you think, "You know, I hate wasting another moment of my life thinking about this old stuff--I just want to live my life for me as though this had never happened," that would be the time you could talk to your therapist about exploring forgiveness.
Meanwhile, please be very gentle with yourself. Your were denied proper nurturing as a child, so be that nurturing figure for yourself now. Trust me, the pain you're going through will be worth it once you get to the other side. You're a very strong person to have made it through everything you've gone through--blessings.
