Nicky! First take a breath and calm down!
Now.. I'm in a similar situation as you. My question is, are you paying directly to Sussex or are you doing study abroad through a US school? If you're paying Sussex directly, Andrea (who is awesome with financial aid help here on UKY) used
http://www.teri.org I believe, for her loans. I'm paying my US school, so I applied for an alt loan through Sallie Mae. I'm not sure if you can use them if you're paying directly to the international school. I'm not sure how that works. I managed to fund my trip, which is going to end up costing around $30,000 for the year. You can do it! Just breathe and search the web a bit! Also, don't be afraid to ask a financial aid adviser at Sussex or your US uni (depending on who you're paying through).
Trust me, I know exactly how you feel!
ETA: You might need a cosigner if you don't have your own credit, but I'm not sure. When I applied for my student loan through Sallie Mae, it told me that "first time freshmen always need a cosigner" but I applied as a sophomore and was pre-approved without a cosigner. But, I also have about 5 years of credit established on my own. You won't know until you try and apply on your own first. If it asks for a cosigner, then that will be the next hurdle to overcome. One step at a time!
Also, ETA: Even if they have bad, horrible, or extremely awful credit, you still may be able to use them to cosign. Sometimes different types of loans base it on debt to income ratio, sometimes longevity of credit history. I think it all depends on the place you apply through. I could be wrong on this though!