Hi bigsis25,
I hear you love your brother and I hear your anxiety. It sounds like having your brother back home is really stressful. Take a deep breath nothing has happened yet.
I don’t feel like I can talk to others in my daily life and I feel guilty talking to my family about it excessively or sometimes at all because I don’t want to add another layer of stress.
Have you considered seeing a therapist? Your feelings about this are just as important as those of your other family members, and your anxiety level seems high. A therapist can listen, give you support, and help with coping skills around situations with your brother.
You have all of the members here too

How do you cope with a sibling that has BPD? Cutting him off is not an option though I have distanced myself as much as possible lately.
My first suggestion is take care of you. Self-care is really important... .think of it like being on an airplane and the oxygen masks come down the flight attendant tells you to put your mask on before helping someone else. You can't help anyone if you are passed out due to lack of oxygen. So taking care of you will help you when negotiating issues with your brother. It is not selfish to take care of yourself.
Can you elaborate on the kinds of behaviors you and your family are seeing when it comes to your brother? We have a lot of tools that we can share and the members here have probably experienced something very similar. I was amazed when I first arrived here at how similar all of our stories can be.
I’m trying so hard to understand what goes on in his head... .
Have you done much reading about BPD? I found it really helpful to get a better understanding of the behaviors I was seeing. Everything feels so chaotic but once you understand BPD a little bit more it's easier to see what is going on under the surface, why your brother might be acting the way he is.
Two books that I liked were...
Stop Walking on Eggshells: Taking Your Life Back When Someone You Care About Has Borderline Personality Disorder by Paul Mason MS & Randi Kreger
Overcoming Borderline Personality Disorder: A Family Guide for Healing and Change by Valerie Porr
Before I go I also wanted to point out the box to the right --> each item is a link to more information, please check out the "Lesson" section when you get the chance.
Hang in there,
Panda39