Some quick context: I discovered pretty recently that it's very likely I have BPD. Unfortunately I don't have enough money to get tested for it, but I've done a lot of research and I meet nearly all the diagnostic criteria. I still am not 100% sure, though, so I just say it's likely that I have it rather than saying I definitely do have it. If this upsets anyone here then I'm sorry. 

But because of how recent this discovery is, I'd like some advice from people who have more experience with actually knowing they have this disorder.

I'm also sorry for how long this post is, because I guess it's also a bit of a vent, since this is the only place I feel safe talking about this. If you want to get to my main question, it's in the very last paragraph.

One of the biggest problems I have is the whole FP thing. I get attached to specific people and get very obsessive, and I don't know how to handle it.

I love my best friend so much, but I hate being so obsessive. Nearly every night when I'm trying to sleep I'm overwhelmed with feelings of how much I love her and how badly I want to be with her in the present moment. Sometimes I even start feeling like she can treat me however she wants because I'll love her no matter what. I feel like even if she abused me I would still stay by her side forever, because she's done so much for me that it's only fair. I feel like it's my duty to protect her from every bad thing in the world, and if someone hurts her then I feel like I failed. It feels good to fantasize like this, but at the same time I hate how alarming the thoughts are. I want to be able to love normally. 

I think the splitting is the worst part. If she gets mad at me (and sometimes she isn't even actually mad but I interpret it that way) I spiral very hard and start to cry because I feel like she hates me, and it causes really intense feelings of self-hatred. And then I get angry because I feel like she doesn't care about me and I start hating her for that hour or so. It's so awful. I don't want to hate her.

She already knows about my obsessiveness because I told her at one point, but I've made a promise to myself to never tell her how deep my thoughts and feelings actually get. I don't want to scare her away and I don't want her to feel like I depend on her. I don't want her to feel like she's constantly walking on eggshells around me because of how sensitive I am. I want to have a normal and healthy relationship. The last thing I want is to feel like a burden or annoyance to her because of how clingy I am.

I know it's silly to ask about this because I'm sure many of us have the same question and are still looking for the solution. But if anyone does have any tips, please share them. 

I want to know how to handle these feelings. I tend to keep them mostly to myself, but I don't know if that's healthy because I know how bad suppressing emotions can be, and I don't want it to turn worse. But I definitely don't want to act on them either. Is there anything I can do to make this whole thing more manageable and make my relationship more stable?