Differently Treated

My step dad has been there for me for almost eleven years and yet he still treats like im not one of his own. He hardly ever speaks to me the only time he ever does is when i start the convo or he wants somethin or wants to have a go at me. He dosent even say goodnigh to me anymore.he knows how much it means for him to be a dad to me because when i was 2 my dad left me and my mum and i have no clue who he is. He has been promisin to adopt for ten years but he only said that to get on my mum good side and nothing has been done about it. This christmas he proposed to my mum and ever since that my mum has treated me exactly how he treats me and whenever he is around i feel worthless and all of the other kids and little angels ... i just thought it was coz u am the oldest child in the house now but i dont understand why my step dad dosent like me and now he is makin my mum hate me too idont have a clue on what to do any advice would be great thanks