I need advice regarding a federal student loan.?

A few years ago, my daughter asked me to co-sign for a student loan. At the time, I was married and had a two income household, so I co-signed. While she was in her first year of school, I left my husband and filed for divorce. I moved to another city and my financial status decreased. My daughter had some health problems and had to quit school. She could not work for a long time, so I contacted the agency and explained the circumstances and they put a deferment on the loan. A few months ago, they contacted me and said my deferment had ended and I needed to begin payments. I explained that I could not afford the payments and asked for another deferment. They refused and I got my first bill. I called again and asked if someone could assist me with lowering the payments or anything else. I was told that I needed to speak to the IRS. I didn't really understand what the IRS had do do with it, but I called them anyway. They told me that they didn't understand why I was calling them. I can't get anyone at the agency to help either and now I'm getting late pay notices. What can I do?