Child support

My question how much is the exact or estimated amount for child support? I have an 8-year-old son and his father works as chief engineer seafarer from an international company. Monthly my son receives ₱7000 every month for his food, and allowance Occasionally he gives 1,500-3000 which only happens if I beg for financial help like medicine and clothing. We don't have a formal agreement regarding this matter because use he doesn't want to talk personally or legally when it comes to child support. I paid alone for our house rental, household, Laundry, and utility bills like internet, water, and electricity. There was a time year June 2020-April 2021 when he didn't give any child support for a whole year and imagine the burden and suffering I felt during that time of pandemic. Way back in 2019-2022, my child received ₱5,000 as child support so I asked for an increase since the inflation is unbearable so from mid-2022 up to the present my son receives ₱7,000. So my question is it is reasonable, especially the necessary needs and all are now expensive? We lived together from April 2014- November 2019/5 years but I didn't receive any amount from the property he sold to think he was the one who forced us to leave the house and accused me of anything and I suffered from verbal, emotional, physical, and now economic abuse. Does anyone here can help me with my case? I seek help from lawyers here in my city but I guess I asked the wrong person and I'm so frustrated right now in my situation since almost 4 years now there's been no justice for me and my son. by the way, we're not married we just lived together for 5 years as common law and my son is an illegitimate son since he was annulled on his marriage when we met.