Supplemental insurance-how do you get it?

My medical bills are through the roof, and my primary insurance just isn't covering enough. I'm in college, so it's hard for me to come up with thousands of dollars to pay for all the stuff I need to treat my disease. I was wondering if anyone has, or knows how to get supplementary health insurance to a major medical plan? Any advice would be great! Take care.

It is actually 7.5%, sorry.