Im so fucked (depression)

Im so behind its not even funny. Ive fucked up again in one of my classes and missed one i was supposed to go to. I can feel the depression getting a grip on me again but i dont know how to stop it??? I hate this fucking disorder because it just slams me out of nowhere and i'm not me anymore. I get these really long Bipolar depressive episodes and I have no idea what to do and everything is slipping. I only have four classes but i cant even keep up with that and I have six next semester. I dont know how to function. I'm not cut out for this but I have to do it in order to even survive, but part of me doesn't even wan to do that anymore. I just wanna let it all go to shit. But i know I wont feel that way in a few months so I cant let the self-destructive apathy get the best of me. 

Idk i just feel so...hollow??? Like nothing matters and its hard to make myself care about schoolwork or even focus because what the fuck does it matter??? Do good in college to get a piece of paper so that i can have the job i want and then i what? Inevitably die like everyone? (i know this sounds so fucking pretentious but like...idk it just is the way it is) theres no end. There'll always be more and more and more and more to do and I cant do shit about it. So why do any of it at all? after college itll be my job and after my job it'll be other things that need me and something always needs me, needs me to do something that i cant avoid because then  my future goes down the drain but you always have a future right up until the second you die, even if that future is only having a few seconds left.

I'm fighting some serious self destructive behavior right now and its taking all my energy, so i feel like i have nothing to give to classes. This is all exacerbated by my physical problems getting worse and worse as time goes on. It's hard to be excited for a future that only seems to contain pain.