I'm in a tough situation right now & in desperate need of advice.

When I was younger my parents were already divorced I have no memories of them being together & since then I’ve been moving place to place with both my younger & older sister.I always felt like the odd ball..My older sister was there first born so she got attention, then there is my younger sister who is there baby who got a lot of attention as well. Whether they noticed that I felt left out or not doesn’t matter to me anymore. Well my older sister is 18 & got preggie at 17.. My neice is about 7-8 months old & I’ve been really been put through a lot of stress. While still moving from my moms house to my dads house to my grandparents house to my friends houses or sometimes even at desperate times at total stangers houses.I currently live with my Aunt & everywhere I seem to go I’m never happy.. Always depressed &thinking about a lot & well my dad’s ex wife legally is still his wife which is my step mom uhntil they fully are divorced has recently offered me to live with her. Before then I was homeschooled.. doing nothing all the time. MY step mom thinks it would be good for me to go to a regular school so I can have a social life& go through the highschool stuff like prom & graduation. Well I talked to my dad about it & he told me how bad of a person she is… or was for not liking me or my sisters when we were younger so he told me to talk to her more & know the truth .. I’m not a person who dwells on the past so I dont really care about what has happend then. I made up my mind to live with her. Now my dad has told my aunt he won’t allow it. I don’t know what to do.. because before I ever thought about living with her he didn’t seem to care where I was.. There is so much more to it .. but from what I have said I could really use some open minded advice. Thanks xx