Hi,
sorry to hear about your situation and hope you get it sorted asap. It seems you've fallen for the PPI hype and moreover failed to read the small print in the agreement which you signed when taking out the card. Companys selling this kind of 'protection' often come under scrutiny for their underhand tactics in getting you to sign up or expoit a loophole as you have found out. Check out the link to Money Saving Expert, Martin has a lot of advice on PPI.
In this case why not contact your card issuer and explain the probelms you're having. They may allow you a period of grace to get yourself sorted out finacially. In the meantime do not spend any more on the card as the interest rates charged are about 3-4 times as much as a loan. ( credit cards charge between 22% and 30% p.a. a low cost loan would be around 7% p.a. )
These websites offer good financial advice and tips on managing your money. Good luck.
http://www.moneysavingexpert.com/
http://www.fool.co.uk/