Hi Fishee
Welcome to the website. You've come to a good place where you can honestly and anonymously share your story. That's important. As Arleigh said many of us have been where you are today. Post here as often as you want. Writing things out will help. Read here as much as you can, you will be amazed at how much it all sounds very familiar.
You have a lot of things going on, many of them are what I would call the big ticket type issues. If I were you I would feel confused, scared, angry, rushed and pressured. It's very hard to sort through these types of issues when in the middle of an emotional whirlwind. Take a couple of deep breaths. We will be here as long as you need us.
Fishee what I noticed first was what you called the scary and dangerous part. All of us would be frightened by what you described. My own personal rule is safety first. Safety first. My relationship had strong elements of violence in it. There was a ton of conflict. Over on the right hand side of the screen in the banner there is a step that talks about stopping the bleeding, diffuse conflict. When you are ready take a look. I had to learn how to safely and calmly take a time out before arguments and rages reached dangerous proportions. Does that make sense? I had to learn to say to my partner, I want to talk to you about this, it is an important topic. Right now I am overloaded and upset and I need to take a break. I will be back to talk more in ... .a day... .two days... .4 hours. Whatever fit the situation. Saying something like that worked better in the long run than saying 'you are acting crazy, I am out of here.'
That's some times pretty hard to do. There is usually a lot going on in these volatile conversations, and she is not going to willingly let you leave the conversation. If the best I could do was say, I got to take a break as I was walking out the door, that was fine because it is safety first.
I noticed you said you have a therapist.

Excellent. That is a very good thing. Having a support system around you, therapist, parents who understand are all good steps. You are doing the right things.
Buying a house, having a kid. These are all big ticket issues. Tough things to do when everything is going well. Stopping to consider if this is a good time to go all in is wise. I like what hmmmm said, is there a way to slow things down for you? A way to ease up the pace of things that won't add to the intense emotions already in the mix? What do you think? You are perfectly within your rights to say 'partner, we've had a lot going on lately, I feel that I need to take x amount of time to re-organize my thoughts'.
ArleighBurke also mentioned that it isn't usually recommended to tell someone about BPD right away. In the beginning you are still learning about this disorder. In the beginning feelings are usually still pretty raw. Almost everyone arrives here in crisis of some kind. I did. What is suggested, is that you respond to symptoms first. People smarter than me told me to discuss the symptom first. I used to say ( a lot) I'm noticing that this conversation is getting upsetting, I don't want to fight with you. Just to lower the temperature.
Tell us how you are doing today? How have things been since you posted? We care.
'ducks