Hi, Boisnix79, and welcome to this board.
It sounds like you are going through a lot right now. A breakup can be a lot to process, and it sounds like you are also going through a Breakthrough Crisis as well (See step one of the Survivor's Guide---> There can be some intense emotions during this time, and it's important to take care of yourself.
I'm so sorry to hear about the abuse you endured as a child. :'( It was not ok for your mother to hit you, and it was not your fault. It sounds like she made you feel unwanted. Every child needs his parents' love, and I'm sorry your mother neglected to give you that. It sounds like your grandmother was able to help you by providing some real support and affection, and that is worth a lot.
You probably have already learned about "splitting." Many parents who have BPD split their children; one is often "all good" while the other is "all bad." It sounds like you were assigned the "all bad" role. This is arbitrary and has nothing to do with you or your value. However, your mother and perhaps others who learned her way of thinking may need to continue to see you this way, and there is probably nothing you can do to change that. By having someone she can project her own issues onto, she can avoid taking responsibility and experiencing shame herself. Children who have been split "all bad" often experience deep feelings of shame and depression. This workshop may have some helpful information for you:
Toxic shame--what is it and what can we do about it?I lost my whole FOO, i have my grandma aunts and cousins but my hearts still broken... .
Do I lat down, take the blame to have them all back?
I think it boils down to your values and boundaries.
BOUNDARIES: Upholding our values and independence Another question to ask yourself is whether doing that would make you feel better. What is the goal you want to achieve?
Wishing you peace,
PF