I want to thank all of you and am also in a need of help

So, first of all hello everyone! I am new here but I have been lurking for a while now, reading the posts the others have made. What I love about this forum is the intelligence of most of the people here, I can really see myself in these posts where you guys describe your fear of abandonment, need for care and acting almost (who am I kidding, just like ) a child to receive it. Thank you all for sharing your most embarrassing parts of this disorder in such honesty. It helps me realize I am not alone. It is so humiliating when I, a grown up intelligent woman, am acting so irrationally and childishly and in my mind I put myself down a lot for it. This forum helps.

Speaking of help, I need some... advice? Thoughts or maybe just some personal experience.
I was in a relationship with someone for a year and a half. And when I say relationship, I mean "childish dream of a future relationship with a person who is no capable of any real intimacy". It was emotionally abusive and sick, I guess we both were ###$ up but in my defense the people who are ###$ up pull the worst out of me too. I tried to act rational most of the time but I made some grave mistakes too. The person I was with was most likely a bpd/npd hybrid. He even admitted it once that he suspected he was a narc. He cheated on me twice, made empty promises, left me only to want me back again and all that $#%^. I threatened to leave him too many times but never really did.
Anyway, now it's been three months since we last spoke and I am starting a new relationship with another person. I find myself being overly scared of being hurt again and afraid to attach. I like her (she is a woman) but it's not the same magnetic pull I felt towards my "ex" or whatever that person was. I guess what is lacking is the famous bpd-npd dynamic I had with him. This is healthy and good, I like her and want to spend time with her but I don't feel like I NEED NEED NEED her or I'd die. I don't feel like she could (or should) be the bucket I can throw all my pain in. I just don't know how can I completely forget the person I was with. How can I make myself fully WANT TO be in a healthy relationship instead of having this constant push and pull game of a npd/bpd? One minute they're all you ever wanted, the next they betray all the promises they made and hurt you.
And another question, how do I make myself trust this new person she isn't the same as him? That she won't hurt me in the end and that she likes me the way I am? I am constantly scared she'll realize she could get better and leaves.

As far as trust goes, it's not something that you "make" happen. It's not something that should be there in the beginning. Trust is something that is gradually built up over time IF the person teaches you through their behavior that they deserve to be trusted.

The vast majority of people on Earth, including those of us with BPD, want a healthy relationship. A lot of people (often including people with PDs, naturally) just don't know what a healthy relationship is. We instinctively want it, but we can't consciously define it or recognize it.

So then entering from the other side of the psychological stage is familiarity. There is comfort in what a person knows, most of the time, even if what a person knows is unhealthy or otherwise bad. This is just human nature, and it applies to most people, including people without any sort of disorder at all.

So it becomes a battle between what we instinctively desire (healthy relations with other humans) and what we actually know (and in the case of many people with BPD, what we know is dysfunctional, abusive, crazy $#%^).

SO commonly a huge part of settling the matter for better (instead of worse) is to learn about healthy relationships, through therapy for example (with a good therapist, not a $#%^ one), until what is healthy becomes less and less mysterious and bizarre to us.

An example with your post is the concept of trust. Nobody should be demanding your trust, you can't make yourself trust, and trust isn't even something that is supposed to be decided. Again it is gradually built up over time IF a person's behaviors show you that they deserve it.