Foreign Territory

I have BPD. I've known I have it for a long time now. I don't tell anyone. I found someone that I trusted enough to tell, they shared their secrets with me and I shared my own back. We've been seeing each other as friend's for a long time, but I think I have a crush on them. With my BPD, I often find myself getting obsessed or attached to people, but this person is different. It usually feels like fireworks when I get obsessed with someone, but with this person I feel like I'm slowly melting. I think I genuinely like them. And that's new to me. What's worse is I think they like me too. The point is, what should I do? I'm too scared to tell them; I don't know what I'm capable of. I don't know what I would do or how I would act in a relationship. Am I even capable of having a stable relationship? Should I step down?