Sadly that is the case with medicine, it only helps you so much, the real fight against anxiety in the end is all down to you. The therapist you've seen has probably helped you to find out what causes the anxiety, so knowing that will help you to beat it and come out on top.
As for dealing with your anxiety at the moment, i know when i used to feel like that i used to write. I would sit down, fingers on the keys and close my eyes and imagine a new environment. I'd make that real and write down what it was like, write the events that i saw, words spoken, etc. My anxiety used to calm down after awhile. These days i find running and kata a way to calm my mind.
From looking at your work i can tell you have a great imagination so might be worth a try next time you feel that fear coming over you. Take yourself to your sketchbook/laptop, take your drawing tool into your hand and close your eyes. Imagine yourself in a more relxing place, make it as real as you can inside your mind and lose yourself to it. Sounds insane though when i write it lol.
Don't give up on your dreams, your in a place you've always wanted to be so remember that. Remember how great you felt when you first heard you got into your uni, how great it felt to meet your amazing friends there and remember those great times you have with them. All the negative will pass.
Talk to a professional so that you can get the anxiety and depression under control. That's the most important thing you can do right now. You don't have to leave school, but even if you took a semester off it wouldn't hurt you. Depending on your loans, some of them have six month grace periods before you have to start paying anything back.
Your situation is actually really similar to mine. I went to an art college with a very demanding and stressful curriculum, and ended up leaving at the end of my third year due to untreated anxiety and depression. I didn't start getting help until somewhat recently. I wish I had been able to finish school and get a degree and all. I hope that everything works out for you.
Rachel, if you're school has counseling you should talk with them about this. At my school at the Academy of Art University we had counseling for students who got behind in schoolwork and needed help. It sounds like the depression you are dealing with is serious. Bottom line, there is no reason for you to go through what you are feeling all by yourself.
When I was at film school I and many of my fellow classmates had hard, lonely times, especially during the holidays. There were times when I couldn't handle all the work that was thrown at me and I had several meltdowns and even had to quit my job at the disney store to deal with the stress. I know it can be very hard to get through. If you ever want to talk about it, feel free to PM me and I'd be happy to listen. You are a gifted person and I believe in you.