Managing BPD symptoms in an LDR

Is anyone else here in a LDR and dealing with constant feelings of loneliness and fear of abandonment? I see my s/o 1-2 times a month for a few days and we text briefly everyday, but I am struggling with something called "object permanence". Basically I have a difficult time feeling like the relationships is "real" when he's not around, which causes me to withdraw (from him and others) or become extremely anxious. At times (like now) I just won't respond to his texts. I'm still not sure what the point of this behavior is, but a part of it is I feel guilty for always being so down. Distance doesn't effect him the way it does me and he's much more social than I am, and in general, a "happy" person.

I am in therapy to address my BPD and he has on occasion joined me in my therapy sessions, which has been helpful. I have a difficult time letting go of incidents in our relationship that ranged from him cheating on me, to chronic lying. I often ruminate over these while we're apart and am using skills I've learned in therapy to not react to these feelings and try to self-soothe.

I think the hardest part is going home to an empty place and waking up alone. This brings a lot of intense feelings of loneliness and anxiety that we'll never "close the gap" or I'll be alone forever. I have a really tough time connecting and meeting new people, coupled with extreme guilt about my BPD that I sometimes really believe I'll never find anyone ever again (which has caused me to latch on to unhealthy romantic partners in the past). It also causes me to constantly question if we should be together, simply because he's not around enough.

Anyone have advice or good coping skills for those of us in LDRs? Or even dealing with very persistent feelings of loneliness and hopelessness? Or thoughts on what made you realize it was time to call it quits and move on? We have (for now) made a commitment to try to make this work, but even after a year, it's not really getting any easier.