child support for non married

Hi,

I'm not married to this guy but we lived in together for almost 6 yrs and we had 2 kids 11 yrs and 9 yrs old. We separated almost 7 yrs now because of his infidelity and since then we dont' have any contact and he never communicated on our kids. He has a wife now and they were married and has kid. But ever since we separated my kids did never get any support from him and I want to get this now since my kids are growing and there expenses is growing as well so I want some help financially. I seek advice and went to DSWD and they told me that it is impossible for me to get support because we are not married and my children surname is after mine. I felt sad when I here that statement from them because I feel that I cant be able to fight for my children's right anymore, but when I do my research about RA 9262 and what they have told me is not true I can still be able to get child support from my children's father.
My question is how will I start? Some say I should go to my ex Brgy. for us to set agreement and settlement for the support. Some say I can go directly to a lawyer to get Demand letter first and if ignore by the other party that's the only time to file for a case against him. I am now confused on where to start. Who is the best party to reach out? Will I get subpoena or demand letter once I have provided my statement and story to PAO? If I will file a case should I go directly to PAO since I dont have capacity to get a lawyer?
Please help I need an advice so badly.

Hi,
Single mom po ako of a 7 years old. Ang father po ng anak ko ay 7 years younger sa akin. Graduating student po sya ng mabuntis ako dahil magbarkada kami,but after 1 year ng live in namin kung kailan siya nagkatrabaho saka niya kami iniwan ng anak ko dahil sa 3rd party namin na hiwalay sa asawa at may 3 anak. Gusto niya po magsustento before pero hindi ko po tinanggap dahil kaya ko naman suportahan anak ko. Nung nag 5 years old na po ang anak ko siya ang mismong nakipag usap na gusto niyang suportahan ang bata pero walang amount na pag-uusapan, ang problema po pahirapan naman magbigay, lumapit po ako PAO ang gusto nila ay P2,500 per month ang ibigay ng ama ng anak ko 3years ago, pero hindi ko po pinirmahan. Sa ngayon po typical na empleyadona lang ako na sumasahod ng minimum, ang gusto ng ama ng anak ko ay maghanap ako ng ibang trabaho para masustain ang pagpasok ng anak kosa private school. Wala po akong nakukuhang sustento sa kanya monthly although sagot niya po ang P34,000 na tuition at service na P700 per month ng anak namin. Sa sinasahod ko po hindi talaga sa ngayon kinakaya ang gastos sa pang araw-araw, may timepo na pag sinabi ko po dun sa ama ng anak ko na gipit ako, lalo na pag may sakit yung bata pahirapanpang manghingi pambili ng gamot. Nagtatrabaho po siya sa isang call center at may mataas na posisyon na din po kahit paano. Ask ko lang po na sa ganitong sitwasyon hindi ba dapat 40%na income ng tatay ay dapat napupunta sa bata. Sana po matulungan niyo po ako, salamat po.