I wish I could help but it's hard. Maybe bring up the 9 traits of a BPD person and show it to him when he's in a good mood. Don't be surprised if he turns on you and instantly denies it, but it may open up communication with him. Most BPD's refuse to admit they have it and it takes a while to admit it. It is a gigantic sign of weakness; shows us that we're "bad" on our black and white way of thinking. I'm not saying he is or isn't BPD...but that is worth a try. Let him know you're worried about him and you want things to work out for him and both of you. And know upfront that a BPD's biggest fear is of abandonment and they have very poor if not non-existant relationship skills because of it. They inadvertently cause what they fear the most. Keep these things in mind when you talk to him, but you HAVE to talk to him, regardless of whether it's BPD or not. There is a forum on PC specifically for people in relationships with people with personality disorders. That may also be of use to you. Wishing you the best of luck.