For context, I have been professionally diagnosed with bipolar disorder with psychotic features, borderline personality disorder, general anxiety disorder, and insomnia. I am 18 years old and am in college studying philosophy to become a lawyer.

I have always been considered gifted. I'm good at math, english, science, history, and everything inbetween really. But, my constant lack of motivation is hurting my grades horrendously to the point i'm not sure what to do. Even if I'm good at something, it means nothing if I don't apply myself to learning it.

Treatment unfortunately hasn't worked for me, most medications give me serotonin syndrome or do absolutely nothing. Therapy is a great thing for many, but has never worked for me. I feel like I'm really stuck in a painful place where i'm progressively getting worse and nothing is helping me get better. I abuse sleeping medication and alcohol to keep myself functioning, but it doesn't help anymore. 

I really have no motivation, it's finals week and an important exam is coming up. Though I'm good at the subject, I never applied myself to the class. I really should study for it, but cant seem to bring myself to. I sit down, ready to study, and just can't. I'm so drained, I don't know what to do anymore. I'm panicking inside of my head, but I cant seem to focus on a single thing. It's as though my mind is desperately screaming, but I sit motionless, doing nothing. I can't focus no matter how hard I try, and eventually I just end up staring blankly at my ceiling, dissociating for hours. 
I'm going to try again tomorrow night, it is very late where I live and I have a unfortunately busy day tomorrow. 

Does anyone have any advice for dealing with lack of motivation, or disassociating when attempting to do something important like study?

I'm sorry if this post is a little scrambled, my mind is everywhere right now.