So for a while now I've been suspecting that I have BPD. Ita come to my attention that I had been showing a bunch of signs, but they were just labeled as me being dramatic or sensitive or just plain moody. 

First off, the idealizing and devaluing (this has probably affected me the most). When my family and I get along, I feel nothing but love for them. But if one minor disagreement or argument starts, my mind goes crazy. I start wondering if they even care about me, or is i should cut them off, or if they're actually bad people. It has also affected me being able to keep romantic relationships steady. Whenever my partner and I aren't arguing or anything, (which eventually becomes rare but I'll get there) everything feels like fireworks. I see them as this amazing person, who I would do a lot for, and who I love a lot and could never leave. But when they make a mistake I explode with emotions. I start saying hurtful things in the moment. Many of my relationships have been ruined by me starting constant arguments. I start wondering if they ever loved me in the first place, and I assume that they meant to do it all along. But within less than an hour or 2 everything feels fine and I start idealizing them again. 

The mood swings. Whenever I explode on someone out of anger, of course I'm very upset, but any small thing can make me happy again. Today one of my brothers was annoying me so I slapped him, and we started getting physical. My cousin broke up the fight and he said something so simple that made me just laugh and happy. My family members have commented that I'm "bipolar" and I have massive mood swings. If I'm happy, something can easily change it and make me upset. 
Speaking of mood, the intensity of my anger is disturbing. One little thing sets me off the rails, and I'm ready to fight someone. 

The impulsivity. As I mentioned before, I say things in the moment, but it's more than that. I say other things and mean it in a kind way, but it's not until I've already said it that I realized that what I said was impolite. I remember one of my relationships was ruined because I gave them a loyalty test. But it just doesn't stop there. I've made many impulsive decisions, that I wish I hadn't made. I dyed my hair twice, cut it once (really short and it's still growing back), spent an unreasonable amount of money on things I don't need, ended friendships and relationships, etc. 

The dissociating. There's many times where I wonder if anything is real. This makes me zone out. I think that's all u really have to know. 
The "favorite person" thing. Like I said, I have a habit of idealizing and devaluing them constantly. But it's like I develop this very unhealthy attachment to them. My mood depends on how they treat me. If they leave me alone even for a bit I feel lonely and unloved. If they get upset at me, I feel heartbroken and rejected. I overthink constantly about their real motives and if they really adore me or not. I become extremely clingy. I test if they really love me and are faithful. 

I understand that this is toxic behavior, I just seriously want to know why I am like this.