Blank mind is kind of subjective experience that only causes problems if you obsess over it. I'm sure something real is happening in the brain to cause such symptoms but you have to ask yourself what problems is it really causing you. People will say they can't do anything on account of blank mind but these are often people who don't try to get employment, enroll in classes, or frankly do much of anything. Many are suffering from depression and anxiety.
Since you're having real problems in your life "I can't socialize with people, barely function in school, and have trouble getting in job applications," I think it could be a good idea to figure out very precisely what is going wrong, and how the problem might be remedied. Many people from DPSH become overwhelmed and then don't do anything for hours at a time, functioning just breaks down for a time. I'm somebody who does this, loses hours of the day not really relaxing but just staring into space and wandering in my mind. It can be very challenging to maintain functioning with a disorder, compounding with the stresses of life most people go through.
Tell me if I'm wrong but I think most people have some idea of what would make them feel better. Sometimes people orient themselves towards obsessions or misguided goals but basically who am I to tell you what will make you feel better? I can only make suggestions based on if you volunteer more information and my suggestions can also be wrong.
I'm sorry therapists and psychiatrists have been useless in regards to depersonalization. In my experience psychiatrists usually change the subject and therapists will default to some simplistic notion like coping skills. Coping skills can be helpful but basically there's no proven protocol to fully alleviate depersonalization. The best results come from improving overall physical and mental health but even then chronic depersonalization has a nasty habit of sticking around no matter what. The severity can and often does fluctuate, getting worse in times of more severe stress.
