Please help me

I feel far too embarrassed, and humiliated too speak to anyone about this in person, and I seriously need help here. I'm being completely delusional, and I'm fully aware of this. I genuinely feel like I'm losing my mind, and I feel so ashamed. 

So, I'm just going to get into this before I chicken out. I've been obsessed with a  person online that I've never even met for the past 2-3ish weeks, and I don't know what to do. I've only talked with them like once. One moment, I absolutely adore them, then they post something I don't like, and I hate them. This has become a cycle, and it's ripping me apart. 

Their all I think about, and I've built up this fantasy of them which I know isn't how they truly are. It's gotten too the point where I've started to unintentional change myself in order too be what I think they'd like more. I can't control it. I'm losing track of who I am again, even though I've never known who I am, trying too be something I think they'd like more. I'm fully aware I'm being delusional here, but I don't know how too fix this. I feel like I'm going crazy. 

I think it's important too mention that it's been suspected that I suffer from BPD by therapists for the past few years now, and I'm looking too get help. The biggest problem has been that I'm far too ashamed too talk about what I feel, and how I think because I know it's wrong. 

I have no intention on interacting with this person, and I'm completely aware of just how unhealthy this is as well as just how crazy I sound. I've been this way in romantic relationships as well, and sometimes just relationships in general. My relationships have overall not been healthy. 

I know I'm not alone in this, and that other's have been through this to. Please, had anyone else been through this? How did you get through this? I just feel like such a bad person, and I just want this too go away. I'm desperate.