
I'd like to welcome you here

By what you said - it certainly sound like you found the right place. Many of us struggle with the same confusion from being with someone who is awesome one minute, but nearly impossible the next. And you are right, it does wear you down. The information on this website can help you restore some order to the chaos. And you will be amongst people who know just how you feel - the confusion, the heartache, the frustration, and the hurt.
Is he actually diagnosed BPD? Or do you just suspect it? Many people seem to deal with pwBPD, but few people ever know that BPD is what they are dealing with.
Again, welcome!