I must admit your post is very well written for a 13yr old Croatian, it seems more adult in the language. However you are concerned. I know that smoking weed in a very common 'recreational habbit' for many people. I know people that do it regularly and have done for years with seemingly no side effects. I also know people who it has effected psychologically to the point it has caused long term problems. One neighbour of mine committed suicide and his parents were quoted as stating his experimentation in college with the drug led to his long term mental illness. Some people are prone to it, some are not. And strains of the drug are becomming stronger, leading to it being re-classified in the U.K. I am not trying to scare you, but state plainly what I think you know. If you are 13 and bright enough to write in the way you have. STAY AWAY from it and I'm quite sure your 3/4 times of smoking it, will in a short time, be nothing more than a lesson learned. You are also bright enough to know that if 'the friend' is a real friend they will except you don't want to smoke it again, if they don't accept it, you should make other real friends too. I think your pyschiatrist has to abide by the same rules of confidence that your Doctor does.
my opinion its sounds like a post traumatic stress from a possible panic attack and ocd. for example when you see your friend it brings back the traumatic event, then you obsess over it. i have had a panic attack and i have felt depersonalization, mine felt like dread and impending doom. Being around certain people or places i become unbalanced, i get severe stress, anxiety and fatigue. the way that has helped me, is face my fears and try to look at things in a different way.
You don't sound like you are thirteen, but if you are, I can't legally answer you so just see your psychiatrist.