@dreamline7,
You're a sensitive soul dreamline7.
Your Mum has done so much for you throughout your life, took amazing care of you, helped all year long talking to teachers, I assume about other kids in the school and now you are more mature you're feeling that she loves your brother more and needs to talk about you, even have a laugh and so, you feel that means she is cold against you, so you need another Mother figure that won't be, that will hold you and hug you.
The thing is, where does your Mother go to get her out let? Standing by you like that for all of your life clearly shows what your Step-Mother has told you, she loves you.
There is a fine line being a Step-Mother, you may love the idea of having a child/ young Adult but, you also are very aware that there is a Mother to that child in the picture, the last thing we are going to do is cause a riff especially when we also know that really, that Mother has done a lot for that child to show support.
This is about you sweet, learning to like yourself more. Perhaps your Father could have toughened you up a bit more perhaps your Brother is a bit tougher than you, easy for your Mum to talk to and I am sure she needs to laugh as well, I mean, she is Divorced on her own tending to children.
If she suggested that you go live with your Dad, it would be to help you grow further into a young man, in my opinion, a Man does a better job one on one.
You say you start silly fights. Have a deep think, she's been there for you for ever. Maybe she needs a hug from you. Maybe she needs " thanks mum I haven't been the easiest child and thanks for all you've done".
You are searching for love yet you have it from both ladies