I don't have an easy answer.

I know that when I was 28 I complete cut all ties with my biological mother (I moved overseas and never told her where).

I used to beat myself up about a lot of things - she was a **** mother, proved unfit in court, lost custody etc. but I'm going to cut to the chase and say -

It's only at that point in my life where I could look back and say these are HER issues, not mine, and I'm not going to put up with this **** any longer that I could truly let go of the hurt and anger I had held on to for so many years. It's hard, I know. But don't ever believe that your feelings aren't something that you can work through until you reach peace of mind about this.