My girlfriend has BPD and I dont know how to follow through on boundaries

[Handabear]

  I've been with my girlfriend for about a year and a half. We've recently been having a lot of issues that seem to have begun once we moved in together and started sharing a space. At first, we had little squabbles just like any couple would, but I fear I didnt set boundaries and follow through, so now we've started to develop a very toxic set of behaviors.
I have minor depression, so I am very easily manipulated, and if I'm screamed at I break down and give up all my boundaries, so my girlfriend has started to take advantage of my emotional distress. I'm not sure how to set healthy boundaries and follow through. Please give tips on how to cope and follow through on your boundaries through the emotional manipulation.

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[Football2000]

Setting boundaries is tough, and easier said than done. One thing you can try is rehearse them in your head. But I know that can still break down if the other person has a lot of angry stamina and can go on for a long time berating you, crushing you.

Another possibility is living apart. It sounds hard but I think it can actually be healthy, and it does not mean the relationship is over either. It's not necessarily a step backward.