I feel for you. I can understand where you are coming from.

You said it had been a long time since you were in a relationship. Well even someone with BPD needs love.
I don't think that we are programmed to live alone all of our lives. As human beings we need to be touched and hugged and admired and validated and that is what a special someone does for you. And we thrive when someone is meeting all of our needs.

Just try to stay reasonable about it. I know, easier said than done. But remind yourself that you are feeling lonely. That enjoying his company doesn't mean you have to become dependent on him. You can survive just fine without him. So if it doesn't work out, yes, you will be disappointed but it won't be the end of life as you know it.

And I am sure you are stronger than you give yourself credit for.
Repeat:
I breathe in my courage. I exhale my fear.