Left in Limbo... Cheating, drugs, depression...affair fog?

Hi Everyone! I am a new single parent and to be honest I have been left in limbo. I have spoken to friends and family with complete honesty and they cant even offer me an answer as to why I am in this situation and what I should do next so I thought I would reach out on here and hope someone else has been through this. My ex and I have been together almost 4 years and have a planned 17 month old. We were living together when she was 1st born at my parents house which was very full on as we were in 1 room but we made it work. After approximately 1.5 years of living like this I asked him to move out as I discovered he was doing drugs and I didnt want any part of it around me or our child. So he moved back home and he worked hard to regain my trust and assured me the drugs had stopped. We were saving to buy a home rather then renting and were very close to our goal so decided it would be easier to continue living apart so we were on top of one another in 1 room which was my idea. So for a few months we made it work I would stay at his mums or he would stay here etc... In October 2014 I became annoyed as it seemed like I was the only one making the effort anymore for him to see either of us, which was frustrating and I felt like a single parent. We were still intimate, talking about the future, he was to put it simply LAZY! In November I had enough of it and told him, I was sick of fighting for the relationship on my own, a relationship between me and him and as a family, he couldnt even be bothered to really spend time with our child which was so upsetting! He would rather hang out with his brother, not his family. When I confronted him about these issues saying I wanted out, he broke down crying, begging me to stay, that he was depressed as he hated his job and living away from us, etc... that we were so close to moving out. So i agreed to give it a go if he put the effort in. During November things were good, he was speaking to mortage brokers, speaking to my family members about how much he loves us and HE was the one initiating these conversations even with me, about having another child etc.... Then the next week... he left us. For the reasoning "Im not happy" nothing more, nothing less. I was like what the.... anyways a week after that we were acting fine he would come to see our child, talk to me, invited me to his xmas party etc.... THEN I found a text in his phone to a girl and confronted him about it, he denied it instantly and became VERY angry as I wouldnt give his phone back until I got an answer. I shut the front door and he ended up smashing the glass holding our child, I took her and alerted the police as he put her in danger. An AVO was placed on him which is now awaiting a hearing end of Feb. He saw her on Xmas day as I offered it for 1 hour supervised as for 2 weeks i heard nothing from him. Xmas day went fine, then after that all contact was cut. Not 1 single call or sms from him to speak to me or enquire about his child. So then I reached out to him (stupid I know) asking if he wants to see her, asking if he even cares about her due to the no contact. Would get no response or something just blaming me for him not seeing her or making contact. Everything is somehow my fault despite I have done absolutely nothing wrong. He wont have a conversation with me about anything! Like he ended an engagement and walked out on his family, with no explanation and no conversation. He is clearly off with someone else enjoying the carefree, no responsibility lifestyle, not caring at all what he is doing to us. I have an exemption from child support due to the AVO so thats a bonus. I have been advised to basically wait for him to file for our child, that way i can keep her and basically have full custody until that point. I am just so frustrated as I know nothing, I just want answers so we can move forward... like will he wake up to himself and have the reality hit of what he has done... to me it seems like he wanted to leave have his fun then come back and commit...but then i found out so he kinda went stuff it... maybe drugs are involved... i just have no idea.... i love him, i know its ridiculous but we never really gave our family a real go and we were actually really really good together. I know all he has done is disgusting and unforgivable but i within myself dont feel its over... i cant explain it. i have a feeling he will attempt to come back, i just dont know! it is driving me insane thinking it over and over, like were there signs this was coming, no. Also his evil sister is in his ear and she doesnt like me mainly because i dont let her control me like she does everyone else. I just dont know what to do, has anyones partner done something similar.... i know i am being too nice offering and contacting him, just trying to show i want them to have some sort of relationship but he is the one making no contact then his sister is saying to me its because i am making it to hard!!! Delusional!! Any advice would be amazing as to what i should do regarding him and regarding our child and regarding my sanity!