The biggest weakness I have, by far

This morning, I got an e-mail from a friend of mine who lives in Australia...she knows how I'm feeling.  She gave me a double hug and probed a little bit, asking if the voices I'm hearing in my brain are part of the problem.
I'm thinking about that e-mail, and it's actually putting me into a panic of sorts because she is absolutely correct.  It started the moment I knew I was falling behind in my courses this semester and was amplified about 100 times when it became obvious that access to my math tutor would be train-wrecked for good.  This week that just finished, I haven't been able to focus because all I can think of is, "How the heck am I even going to be able to put a dent in this pile?"  It just doesn't look like it's even going to be possible without me going insane.
Trying to put together a "piece by piece" plan of sorts could help, knowing how my schedule runs now, but up to now that's only been a good idea until I can't keep up with it...and then my conscience is on me in a heartbeat.  I don't even a chance to stare it down and say, "Don't we still have a chance to clear (insert assignment here)?"
My gut is today this feelings are being amplified really badly as a result of a week where my worries have been so out of control -- it's clear the citalopram I've been on is of no help now -- that to say I've made inadequate progress would be putting it extremely charitably.  This has been the kind of position that has led to sleepless nights or ones with inadequate sleep, and I don't have to be told that right now I can afford no more of those.
I wish I really had an idea of how I could reverse this pattern, because any setback seems to feel like a major loss when most of them shouldn't feel that way.  I have a lot of questions...but no real answers.