How to fix trauma at home no glue no borax

I don't know how to explain the situation that is bothering me. Basically i felt neglected my whole childhood and felt like my sister got all the attention and love from my mom. Now i can't properly spend time with either without getting irritated, and they don't really understand this, they try but there isn't really much they can do, because to them it's just in my head. They don't invalidate it, but how can you help someone when their problem isn't technically real?

I don't have to see them often, but i wish i could. I hate being unstable and unreliable, i wanna be a supportive older sibling, especially because i know that my sister is going through a lot right now, even if she never really tells me or anyone, we can tell. Our problems are quite similar too, but it's like she thinks that ignoring them makes them go away. And i can't do anything, it's everyone's own decision to get help, but i feel like i'm not doing enough in regards to create a supportive environment.

I also just hate being mentally unstable and weak in that way, sudden outbursts of negative emotions aren't fun for anyone, and it completely disrupts my life and relationships. Sometimes i can control them, usually with friends. Not with my family tho, and that is what is quite weird. I get irritated easily, when plans change and people are vague and or uncooperative, but usually it just dissolves and i can continue with interactions normally. But with my mom and sister i just fly off the handle, for completely small and inconsequential stuff too. 

Me and my dad get along, we have similar thought patterns in a way and there's way less bitterness so fights are less common. When we get into arguments it's usually because the whole family is there and i already feel overwhelmed and it's like they're all judging me and i get super paranoid and i spiral, this has always been the case. One on one interactions between any member or my family is more successful than when there's more of us. I always hated the living room for this reason, it's so loud and i feel cornered in a way. There's been one on one fights as well. Best example is with me and dad, he says something absurd and quite hurtful and i tell him that i didn't like it, in an "accusatory" tone so he gets upset that i took his "joke" so seriously, and then he stops talking to me. Last time this happened was when we were driving and he stopped talking to me and just started driving over the speed limit, he wouldn't even look at me. This didn't last long because i did try to explain to him that i didn't mean to be mean about it, i tried to explain my point of view because i apparently misunderstood him. And then we could talk it through and he drove normally again. He did apologize as well, and we talk about it still, i always tell him that i wasn't scared, mostly just confused and a bit irritated because how does a 40+ guy just regress like that lmao, it was absurd. But yeah, i also know how it feels i think, you're just stuck in a way, you can't calm down so you just escalate instead without reason. I hope to fix that.

Normally i can think pretty clearly and i know what's real and i can function, i can go days without getting upset with my family and we genuinely have good gaming nights and dinners or watch movies. But then i just ruin it, last time i was a bit drunk and i started an argument and it escalated, this was between me and my sister so it was quite normal tbh but i still feel bad because it's an unsuccessful interaction that was my fault. I apologized and we did talk it through as well, but still feels bad.

I really wish i could fulfill my role better, i try my best but i wanna be better, my lack of progress annoys me.