Help with BPD

Hello my Fiancé Has borderline personality disorder and it has been really really really hard it has gotten to points were I feel like I have done somthing wrong between the name calling saying things that are my deep secrets that she knows hurts me the mood swings one min loving me and the next hating me I am so lost I have lost myself I feel so depressed and I can't come out of it I am trying to be understand loving caring and feel like a human punching bag!!!! She has no sympathy towards my feelings and how bad she hurts me. No matter what I do it's not good enough I love her and I don't want to give up at all but I feel like I am losing it going crazy like really crazy. My anger has gone through the roof I get crying spells and feel sad all the time honestly I feel like a wussy and then I get mad at my self how do I over come this pain what do I do to make it less hurtful and pwrsonal I am so confused and desperate At this point can anyone help