When tschock said that anxiety and adhd go hand in hand, she wasn't kidding. And I think that the pressure of college amplifies it even more.
This really does sound like the pressure is getting to you. And I understand the screaming - been there, done that. I found that exercise really helped me cope (to a point), so thats worth looking into.
I would definitely make an appointment with your college counselor and let them know what is going on. This is not new stuff to them. And it may well be that you qualify for extra time on tests, etc due to your adhd.
Also here is a pretty good site with lots of adhd info. I choose the link that deals with reducing anxiety without medication. the link is
http://www.additudemag.com/adhd/article/8112.html
And it may well be that you are at the point where you might have to go back on to medication. I have seen posts of people in college who use it only at certain times and thus take the short acting meds. Others who might only take it on certain days due to their schedule, etc. This might be something your old doc can help with or the medical staff at the college so maybe also talk to your counselor about this. The main thing is don't try and do this alone. You sound like you are getting kind of close to being in a place you don't want to be. Best wishes. Let me know if you need more info of any kind.
Anxiety and ADD/ADHD go hand in hand.
I know how you feel, as I suffer from ADD as well.
However, this is the wrong forum for this...so I will now be asking for it to be moved to the ADD/ADHD forum.
See you over there!