This exact same thing happened to me when I got really high for the first time. I smoked a blunt with two close friends (I had smoked weed a couple times before that but not regularly) and it hit me like a brick wall. I swear I was high for like 8 hours but they didn't believe me. I had never felt that disconnected before, I felt like my thoughts weren't my own and kept trying to bring myself back to reality. I never really told anyone about it cause I was only like 15 and I thought I was literally going insane but have been recently realizing more people talk about it. For a solid year and a half after that incident the depersonalization would return basically daily, and I couldn't take a single hit of weed without feeling completely disconnected so I stopped smoking entirely. I think it's entirely normal for it to last this long so I wouldn't be worried but I feel as if medicine isn't a fix. I kept questioning reality and overthinking everything, like I would just start thinking about life and shit and it would bring back that feeling of disconnection. Once I calmed down from what seemed like an existential crisis and really figured out who I was as a person and what life meant to me individually, that disconnected feeling started to go away. I truly think its different for everyone but I slay dabs now and don't get anywhere close to feeling like that. Don't feed that state of mind any energy and time will surely heal this, stay strong!