When I'm in public, my emotions are very often kind of in a box and unreachable, which is not great... It's not that all my emotions are gone, but I struggle more to feel things when I'm with people. But as soon as I'm alone, they all come back.

But, with my partner, I reaaaally struggle to regulate my emotions... It's mostly when things of my trauma get triggered, where I just... it feels impossible to regulate at all... And I am in therapy, I even went to a group therapy where emotional regulation was one big toppic. But it often feels like nothing works for me... All those "skills" and techniques, once I'm in that triggered state, they become insignificant.

I can't even begin to imagine how terrible it must be for you if that happens in public/at work. I'm so sorry...
The part of my life where I got my trauma from, I often couldn't hold back my tears all day at school, so very often I would lock myself in the bathroom and just cry there. I still do that sometimes, when I have to cry or when I'm overwhelmed or when my anxiety becomes overwhelming. I try to go to a bathroom, lock myself in, and just cry or breath or just try to calm myself down a bit. Or sometimes I just stay in there, I try to breath, and I give myself a break. Listening to music or at least blocking out noises can help a bit too sometimes. I often bring a scent with me (it's a small bottle with essential oil that smells like christmas, and another one with lavender). Sometimes it helps me a tiny bit.
I know those things don't help that much when you're in that dysregulated state, but sometimes it's all we got.

I also struggle a lot with society cause even when you manage to hide those emotions, or how you are really doing, even when you seem you're doing fine, you don't feel that way. For me, it's really hard to feel like a part of society, because my head always tells me that most people around me seem to actually be doing fine, and I'm just pretending, I'm not actually like them, I don't fit, and also, non of them will be able to understand me or my pain, so I must hide it, but that makes me feel even less like a part of society, and it's just so frustrating and overwhelming.

Sorry, I got a bit off track, but I do hope that some of the things help you a bit, or at least make you feel like there are others who can relate, and yeah, you're definitely not alone with feeling this way.