unemployed unwed mom fight for child custody

i am unwed and have 2child (2y2month and 2month). i brokeup w/my ex-bf few mths ago. becoz i stopped working after 1st child born and used up my saving to help my ex business last year, my ex agree to support i and child after brokeup, i started to look for job since then. recently he asks me for the child custody, but at this moment i am still unemployed, how can i fight for it? how to keep my child with me? what should i do?
pls help, thanks alot