In New York State how can you get child support when you are legally married to another man????? Please read.?

I was married in 1994 and separated from my husband in 2010 in March. I had a child with my boyfriend which I lived with for 10 months, we separated because he abused me but in Ny my husband is considered legally the father but he had a vasectomy in 1996. How can I get child support from the father my ex-boyfriend or can I?