terminated...

Today, I was terminated from my job. I have never been fired before and could use some advice. I was given a paycheck that paid me until the end of the month. Since I have never been fired before, I was asked to sign -- something like a settlement agreement to receive one month's severance pay. I have no idea?? But if I don't sign it, I just don't get paid for an extra month. So many debts and obligations overwhelm me, much more is my medical condition. I understand that they have paid my premiums until the end of July. I was in total shock. I guess because it has never happened to me, I wasn't quite sure how to react.