What's wrong with me?

Hi all. Sorry to jump straight into starting a thread, but I am feeling really overwhelmed and confused rn and was hoping for some advice.

Ever since I was a child I've known I was 'different.' I was, as my family said, 'sensitive' and 'quirky' which is a nice way of saying I couldn't connect with other children, lived with constant worry and anxiety, cried too much, and was too smart for my own good. Nobody considered my issues serious enough to get me help as a child/teen.
I started self harming at 14 and tried to end my life for the first time when I was 17. After that I got myself some help and have been on about ten different meds and in and out of therapy and hospital for the last few years. I'm currently diagnosed with major depression, borderline personality traits, and social anxiety disorder (although I disagree with that one). I also have symptoms of bulimia and OCD and generalised anxiety disorder but I guess not quite enough to be formally diagnosed or something.

Although I've always been 'high functioning' (getting high distinctions and 6.75 GPAs at university even when I was super suicidal) the last year I've felt increasingly disabled. I cannot focus on anything unless it's high, short term stimulation (e.g. doing multiple things at once, scrolling through tumblr, or doing something I'm super excited by like listening to my fave bands), am easily distracted, but other times I focus so intensely on something that I completely forget where I am and the things around me. My GPA has dropped to a 5.5 and I get credits. I cannot eat like a normal person, stay hydrated or fit. I cannot study anymore and I struggle to do the homework for my therapy (I'm in DBT atm). I want to do things, there are even days where I care about things and am motivated to do them, but I just can't. It's like my brain shuts down and I can't organise the tasks or figure out a way to do them.

I cannot connect with others and the two close friendships I had ages 14-18 and then 19-20 deteriorated for reasons I didn't understand. I'm depressed and want to sleep all the time, then sometimes have short bursts of being hyper and talking about off topic things, jumping from topic to topic, and finishing other people's sentences because I can't wait for them to finish.

I know these are common depressive symptoms but even with depression and anxiety I didn't used to be like this.

What's wrong with me?? I can't talk to anyone irl because my family is...difficult, my doctor doesn't take me seriously, and my therapist wants me to stop self harming before I worry about my grades. I hate everything else about myself; I just want to be high achieving again so I feel like I'm worth something.