Hi lostandconfused6,
I'm sorry to hear the communications break down like that. I know how frustrating that is. I think a lot of couples go through that kind of thing. Add BPD to the mix, and things can get highly emotional pretty quickly.
It sounds like in the example you gave, your partner may have felt guilty about going back on the agreement, so he turned the tables and started blaming you for "crowding" him. From there, it goes to threats of leaving, etc.
I'm sure you are familiar with the communication tools on the site, since you've been here awhile. I highly recommend them. Sometimes they don't seem to work, feel awkward, etc., but with practice they can really make a difference. And they give you a chance to express what
you are feeling, which is very important.
In your example, maybe something along the lines of
S.E.T.: "Honey, I understand not thinking it was important to tell me about seeing your friend. I'm glad you got to spend time with him, especially since it's been so long. Our agreement to tell each other things like this is important to me, however, and I'd like to stick to it going forward."
If the agreement isn't working for him, you may want to offer to refine it until it's acceptable to both of you. But I think letting him know that it is important to you is good for you, regardless of what he does. Does that make sense?
Have you had several incidences of troubled communication recently? Is that why things feel like they've taken a turn for the worse?
heartandwhole