Hi lilij10,
Welcome! I'm sorry that you're going through this with your son. It's painful when you feel like you constantly disappoint someone.
What kind of plan does your son have to take care of himself in the long term? What kind of support do you have for yourself?
You're not alone here. There are many other members with children with BPD, and you'll find that they'll be able to give you advice and support. There are also some good tools that you can use to work on your relationship and take care of yourself. I'd recommend that you start here:
What can a parent do? (for parents of pwBPD).
Hang in there and let us know how you're doing.
-GG