Lyn, wow, I completely understand feeling overwhelmed. The graduation situation sounds incredibly frustrating - I will be thinking of you in the coming weeks and hope the exam goes well. Some of my smartest friends simply do not/did not do well on standardized written exams despite knowing the subject matter well; yet they have done very well professionally in their chosen careers.
(I hate to admit that I was rather the opposite; before college I could usually skate by pretty well on exams but didn't know the specifics of the subject matter well. I didn't really learn to study until college and made it my priority.)
You strike me as being so grounded and intelligent (emotionally as well as intellectually) and I am hopeful that you will be able to graduate even if things don't necessarily turn out with the timing you have hoped for.
I'm very sorry that you have been experiencing depressions. You may have read here that this is something I struggle with too, especially (and most severely) this year, though I've spent the majority of my life since I was 12-13 in periodic severe depression. Since july 2011, it's been a day to day struggle to get out of bed and out of the house and I probably would not have made it through without talk therapy and medication. I really feel for you and hate that you have been going through it as well.
I hope that tracing out some of the patterns of your depression help you also find strategies to get through those periods, or even learn what you can do before bottoming out. Shopping & lack of creativity, lack of satisfaction with my wardrobe (and other things I usually like-favorite books, movies) and retreating from friends and family are all familiar warning signs for me. I'm trying to be more aware of those signs and also more communicative with loved ones to let then know if I'm having a hard time, and if I need anything (someone to listen, or some space to myself.)
I wish I could physically pass on a big hug to you and wish you well. I really hope you will find some relief soon. Please feel welcome to PM me if you need an ear, too.