Dear helleia,
I feel like I understand you very well, I also struggled through a difficult major (but in university) and couldn’t connect to other people as much as I wanted. From what I read in your post, especially from this sentence “However, there are moments when my slowness gets out of hand. It becomes so slow to the point of lethargy and all I can think of are negative thoughts.” I think that you might suffer from depression. Maybe you are allready aware of it, but maybe you think it’s just weakness and can easily be overcome if you “just tried harder”. It’s an easy trap to fall into, thinking that if you only were better, you wouldn’t feel bad. However depression can be very hard to overcome all alone, because it is tricky. For example I am sure a lot of those negative thoughts you have sound reasonable in your mind. As are the high expectations you have for yourself e.g. “I should have been able to adapt enough” “I am annoyed that I still have a hard time to try to join an organization”.

Is there a way you can get counseling at your school? Outside of school? Maybe I am off with my suspicion. Only a real doctor can tell. But I think you could profit from theraphy (CBT is pretty good), to start dealing with your negative thoughts, learn to deal with other people and slowly get out of the lethargy.