Where do I start

I'm sorry, I'm new to this. I have been in denial of experiencing PTSD symptoms for two years, after having been bullied by my twin brother (identic twins) for 10 years, and experiencing a trauma climax event over two years ago. At first I thought it was another depression episode (CHAD since 2017) or some weird OCD relapse, but no medication or therapy for these issues could help. From an outgoing, sociable, relaxed and passionate person, over two years I've become unable to feel any emotions, cut off all previous acquanties, completely withdrawing from the society. I have a feeling my life literally stopped in that climax moment, like my previous self died in that trauma, and now I don't know who I am anymore. Everything may trigger a sudden thought of his (my twin brother's) name, mostly when I encounter a term "brother" or any male, young person of the age we were when things were good between us. I've been also feeling restless, can't feel like home anywhere, and I can't handle any possible noise made by neighbours, which makes me extremely uncomfortable (i.e.: loudy steps on the ceiling, children's crying etc.) As I all I ever wanted is to be alone. Also there is a feeling like I'm living in a nightmare - not like a dissociation symptom, but more like a mere feeling of unease you experience in a nightmare, being there every single moment you end up alone in the room. I know you're not professionals, wanted to ask if anyone had similiar issues and also believed their condition is uncurable - like you were "destined" to suffer and no one can do anything about it? I don't know where to start, if you have any advice, please share.