Piano Proficiencies...in college

Well, as everyone knows, I am NOT a good piano player.  However, we are required to do piano proficiencies here at school. Now I've had over 12 years of lessons starting when I was six or so, but I was forced to do it--and even though I knew it was for my own good, I hated practicing and I never amounted to much. I should also mention that while my teachers weren't too horrible when I was younger (they only slapped my knuckles a couple of times), I always learned songs-not scales. So when I started my proficiencies here, I sucked at scales. However, I made it through and passed both major and harmonic scales within the last year. For the last half of this semester I had one proficiency left--Sight Reading. This is where they through a score in front of you, like a Haydn, Handel or random score from a book and you get a minute to look at it and then you have to play it.  All of the scores my professor put in front of me to practice with for the last semester were from level 2, 3, and 4 books. The score that they pulled out today must have been from a level 6 or 7 book. I sat down at the piano and glanced at the piece. The first thing I noticed was that it was in G Major and I let out a sigh of relief since the last one was in c minor.  Then I glanced over the piece. I was lucky I didn't break down and cry right then and there. I briefly considered standing up and apologizing to my professors and telling them that I couldn't do this. I tried to stay calm, but as I looked for the tricky parts in the piece like I had practiced with my professor but as I looked at the piece, I saw only two measures out of approx. 25-30 that DIDN'T look tricky. Again, I freaked out but tried to stay calm. I stared at the music unable to focus and then I put my foot to the floor and tried to come up with a slow enough pace that I might be able to play the piece at without screwing up too badly.
When I figured out a pace, I looked at the bass clef and then at the treble clef and I realized there was no figured bass, no "one-line" melody, nothing. It was completely chordal. The time signature was 2/2 and instead of the bass holding some 1-4-5 pattern or something, it stayed chordal with the right hand so that both hands were playing different notes/chords on EVERY eighth note. 
My hands were shaking the whole time and I missed half of the f#'s because I was busy trying to find three or four other notes.
Of course it goes without saying that I didn't pass. I made it to the bathroom before I broke down in tears and it took me about 10 minutes to pull it together enough to come out again.
That proficiency test was humiliating and embarrassing. The worst part is that it's my fault. My professors can only try to make me play better, but in the end it's up to me.  I just don't know how.