Can I claim for Child support from a US citizen Father

by Maja
(Philippines)

I'm a mother of 3 year old son named Nathan. His father is a US citizen but he is married. His wife is a Filipino as well and they have 2 kids. We never seen each other now for more than 3 years. Is there any chance I can claim for child support if we're here in the Philippines and the father is in the US? He never signed the birth cert of my son so he doesn't carry the father's last name. Will I be charge of concubine even though we never lived together? He's sending me like $50 EVERY OTHER MONTH and it's never enough even just for the milk. I just want him to consistently support his child with me. Nathan is going through a medication right now due to primary complex. He will be going to a pre school next year. And until now, I never received a single cent after I told him about Nathan's situation. Thanks!