Well, you cannot really expect much from your ex if merong siyang iba pang anak na kailangang suportahan. Kasi, even if the father has an obligation to support their chidlren, they can only give support na they can afford kasi, they also need to pay rent, they need to eat and buy clothes. So, capacity to pay ang pinag-uusapan dito.
It will sound harsh for me to say it, but really, this is the problem if you get pregnant with a man na may anak din sa iba -- hati lahat (time, affection, pati money). So, don't expect much. But the father is still obligated to support his child.
Please consult a lawyer.