My uBPD partner has broken up with me on a weekly basis almost every week for the past two years, all while professing undying love and adamantly wanting me to marry and have children with me... //... How do you cope with it?
Do you want to cope with this? Are you ok to settle in and normalize this behavior as a life style?
If your mom had BPD traits and treated you in unacceptable ways, you had no choice but to cope. But with your girlfriend you aren't locked into those "helpless" coping tools - you can stand your ground. You should stand your ground.
I'm not suggesting that you go crazy right now... .reversing this "norm" will take some planning, some communication, and some slow tightening of the noose of on this bad behavior, and accepting the risk (she may only want you in she can "on you"). Short of this, you are rewarding/condoning it and devaluing yourself infront of her - losing her respect.
As understand it, she has broken up with you for 30 days right now. Is that right?
Do you want to end this type of treatment? Are you ready to stand up?