help!!!!!!!!!!! I don't know if Im being neglected

help im adopted and my pearents were very open to me abuot it but when my younger bro was born i started feeling a bit "left out"

then my younger sister came along and it all just feel apart.My pearents just spent time with them and i would sit out but when i tried playing with my family my bro would say "go away " then my dad would tell me to go play somewhere else for no reason.

then in 2007 my biological mother died when i was 10 (im 15 now)  and at first i did not react but the next day i cried my eyes out and my dad would shout at me saying" you never knew her so why are you crying "

and then this year my mom bought an IPad for herself then my brother and sister would fight about it so she bought them each an IPad(note my brother is 6 and my sister is 5) and i sked if she got me anything and she screamed at me saying that i dont appreciate anything ive got that im just a spoilt little brat.

with all the drama i have gone thru i find it very hard to concentrate for a long period of time and that has affected my acedemics and my last report card was bad and i was called (and i quote )"a useless piece of sh**!!"

my brother has hit me with many of his toys and ocasionaly left scars on my back but when i just flick him i get aslap accross my face from my mother

so please if there is any one with any advice it will be greatly apreciated