a bit long but honestly i need advice. no bitching please

im going to try and keep it as simple as possible and give you a break down of events. as at this moment in time i am DESPERATE for advice as i wont get seeing my legal representitive until tomorrow afternoon. and i am an emotional mess today. i am 26 years old. when i was 19 i met a guy. total scumbag. verbally, mentally, physically abusive. i fell pregnant after 2 years together and left his sorry ass. when our son was born i new he was dangerous and no good. so i stopped contact. but after long court battles he got his rights at 2 days a week. when our son was 2 he was displaying sexual behaviours and maturbating etc. and telling me and my family things his dad was doing to him and showing him. i stopped contact again. my mental health deteriated and i became verym ill. i lost so much weight, was suffering insomnia and felt like i couldnt cope. i got social services involved, and because my son was so young, they had no evidence, and 2 days a week was givwn back to the father. so i felt social services failed me. i went on to deal and manage my depression myself. and finally came out the other side. my son got older and new he could always come to me so i knes he was safe again and the abuse had stopped. i met a new guy 4 years on. lovely man he came across as. but anyway i dont need to get into him. my sons health visitor called for his 4year assesment and my mum filled her in on my past with mental illness thinking it would benefit me. but when i met my new man and fell pregnant social ended up at my door for support for my mental health a bit too late now. i told them. ive dealth with it but they wanted and needed to be sure so advised i seek councilling before they leave me alone. i didnt comply and refused to coperate and so i disengaged and cut them off constantly. so therefore my son and new daughter ended up on child protection register. because of thekm. my health went down again so long story short my hralth gping down meant i wss behind on my sons schooling, his homeworks eerent always completed and he was late alot. but i owned up to it and i kicked myself and have done everything in my power and everything they bave asked. all has been going well except one thing. im prwgnant with a 4th baby ans there wondering how ill manage. also there saying with my kids dad being inconsistent thag it wjill affect my son. so now his dad is jumping on this saying he is going for full custody of my son. is there enougg grounds even for him to get this? to me its absurd when theres no risks or concerns regarding my kids in my care.