Hi @outlander - it was a pretty big day yesterday for you with the diagnosis you were given. Don't let them define you though. You are still the same person you were the day before. In saying that, it may assist you to understand more about how you act and hopefully help you to manage the behaviours that are detrimental to good mental health.
The ways you have been thinking have been longstanding and anything that we have done for a while is difficult to change. Right now, you are fighting doing something different. That's where mindfulness comes in. It helps you to analyse what is really going rather than what your head is trying to make you believe. BPD is characterised by a hypersensitivity. For example if someone walks past you and doesn't say hello, your BPD mind may think they are ignoring you and make you feel rejected and worthless whereas they may simply have not seen you or been so preoccupied with their thoughts that they hadn't noticed you were there.
Whilst you are waiting for treatment options to become available, do some research into ways you can help yourself. You need to really want to manage these behaviours. It's sometimes easy to wallow in a dark place thinking the worst - that way we don't get too disappointed when things don't turn out how we would like them to be. It's a good thing to hope for contentment and to get to a happy place.
For a start, I'd to see you write a gratitude journal like @Determined has done. It's so easy to forget that there are some good things in our lives and instead just focus on the misery. Please try it.