He fights with me constantly and every day is a battle to remind him that therapy is worth his time and efforts.
It could be that reminding him of this is reminding him that something is wrong with him, and it triggers him to fight.
People with BPD tend to feel tremendous inadequacy and a sense of not belonging, which is a function of shame. Usually shame is something members of the group do to others. With BPD, they often use shame on themselves, so anything we do to compound that is met defensively.
One thing, too, about friends that I learned. They want to be friends, not therapists. They don't often have the skills and will want to support you, not necessarily your BF. It can create conflicted feelings for you.
I had to learn that it is a very special group indeed who can support you in the skill development and understanding of BPD. A therapist is very important, too, especially one who is familiar with DBT. You can pick up some helpful skills that reflect what your BF might be learning, like distress tolerance and mindfulness, to model for him as a healthy way of dealing with intense emotions, versus fighting and whatever other unhealthy behaviors he has reached for when dysregulated.
