Is my credit REALLY THAT bad?

I am really frustrated. I have 4 negative things in my credit report: 2 medical bills, a outstanding credit card bill with Citi, and an unpaid internet bill. I am in good standing with my student loans, 2 store charge cards (old Navy and Victoria's Secret), a paid off car loan, and a paid off furniture account. I have an open account with Fingerhut and I also have paid in full good standing with American Thrift loans. My credit score is 419. I don't even know how that's possible. My best friend had 2 car repossessions and defaulted student loans that are now in garnishment and her credit score is even higher than mine. I'm in the process right now of trying to take care of my Citi account, but they refuse to do a payment arrangement with me. The internet bill will be taken care of, and I am going to dispute those 2 medical bills. But I'm really confused about how my credit could be in the 400's, with no defaulted student loans, a never late/paid off car loan. Can someone please give me some type of advice on why it might be that bad, or any advice on what I can do. I'm not thousands and thousands of dollars into debt to consolidate or anything like that. Best answer 10 points. NO TROLLS!!!