how to annul my husband

Hi! My name is Jin. I got married last June 18, 2005 because I got preggy at the age of 20. My uncle stood as my guardian and he approved the marriage though. After 5 years of marriage, I found out that he is a drug addict. I left him and I stayed with my parents. What made me frustrated is that he never gave any child support to my 3 kids. By the way, since I started working I never used my married name and all my legal files are declared single. I want to be out of the marriage with him. I already have a bf at the time and we do have plan of getting married. I never heard of him and as far as I know, he went to Cebu. Its been 3 years that we are separated not legally. How is it possible for me to file annulment with him and how much will it cost me?