I'm a divorcee with care and control of 2 very young children looking for a bto in mature estate?

I'm a divorcee with care and control of 2 very young children. My monthly income is only 2k and maintenance of 1.5k and I'm looking to buy a 3-room bto near my mum's in a mature estate. However when I check my eligibility online on the HDB website, it says not eligible for the bto. How do I appeal? I need a place near my mum's as she's helping with caregiving. I am looking for 2 bedroom for my children to use 1 room and myself to use another in long term. BTO is also greatly cheaper than resale