My question involves a roommate in the State of: Illinois

My boyfriend and I moved in together in February of '07. Our rent was 2,000 a month and we agreed to split it and the utilities. After we moved in together I found out he was not financially stable. He never paid rent! He just kept telling me he would be asking his parents for assistance, but I just found out he never did. He owes me a total of $7,600. His dad did come through with $1,300 two months ago to try and reimburse me. I have been more then patient waiting to get my money back. He moved out in October and has been telling me the money would be repaid to me soon, but that has not happened. I have looked for roommates using various websites, but have not had any luck.
What steps can I take to recover my losses? If I take him to court how much will this cost me? If he is not making any money how will I be repaid? He has ruined my credit and I am in desperate need to repair it. Please help.