[Solved] Leaving my child

Hi everyone. I am writing in desperation really, I know some of you might think what I am doing is wrong but I have reached the end of my tether. My daughter is eleven. My ex and myself spilt up 6 years ago and we have had a difficult relationship. She has been very controlling and has had no qualms about using my daughter to get to me. She has told my daughter many times how bad I am and has tried to tell me how I should behave with respect to my daughter and the rest of my family. She does not respect my boundaries and feels able to comment negatively on every aspect of my life. Four years ago I met someone else and we have had a good relationship. We now live together and have been very happy. Previously my daughter got on well with my partner. My daughter often said she did not want to be with her mother but then often said she did not want to be with me either (my counsellor has said this is common when a child finds she can play on off against the other). My child also thought she could speak to me like her mother did which was often a cause of tension both between myself and my partner and myself and my daughter. I have tried to set boundaries for my ex's behaviour such as asking her to communictae via email so my daughter would not hear how she spoke to me but she constantly overstepped them.
About eight months ago my daughter was being particularly rude so I shouted at her and told her to get in the cr and I was taking her home. We didn't obviously and we made up, everything was fine. We had a day together the next weekend and I have not seen her since.
My ex initially accused me of 'emotional abuse' and said she would fight me for access. We have been through the courts and my ex accepted mediation. I have had no contact with my daughter although I continued to send cards, presents etc.
We have had one session of mediation when my ex refused to be in the same room as me although she told the mediator she was keen for my daughter to have contact ( I don't actually believe this as she could have encouraged it at any time). My daughter is now scheduled to see the mediator.
In the meantime my ex has met someone and is moving away (although she has not told me this). My daughter has also cut off contact with my parents who saw her a lot and sent me a text saying she does not want to see me.
The problem now is that after four years of constant fighting my partner has had enough and our relationship is under threat. I too have had enough. I don't want to force my daughter to see me and I don't want the constant battles with my ex. I have had to seek professional mental health help for the toll it has taken on me. Many of my friends say now is the time to walk away and let my daughter come back when she is ready. It is not as though she is very young and wants to see me.
For the sake of my relationship (which has been the only light in my life) and my health I don't feel I can pursue this any more. I know there is a huge amount of opinion out there saying the child always comes first but at what point do you have to take a step back and put yourself first.
Incidentally, I know there is an element of parental alienation at play here. I have spoke to CAFCASS who have said in court that as neither parent has any concerns about the parenting of the other then they are not involved. Basically, my ex can forever tell everyone she is trying but will never stop trying to destroy me.
Please do not judge me, this is the hardest decision I have ever had to take and I cry every day at the thought of it but my child's parent would happily see me destroyed and if I continue down this path I will end up with a small amount of time with my daughter whilst losing everything else I have worked for. I honestly feel I need some time to rest and get well. Many people have said if I maintain indirect contact eventually my daughter will come round and not to force it. Has anyone else been in this situation?