I love my family and i try to do everything for them, Why dont they help me.?

My dad has never really cared for me,ex:He goes and gets food for his "new" family when I leave knowing I dont have money and live with my 19 yrold bro. When the tornado hit my dads house my stepsiss' and stepmom(who he left me for) didnt do anything at all! I stood outside all day everyday getting donations to help my dad out. I was out there when it was freezing cold and my body was aching because I was shivering and standing all day I was So sick. I raised my dad $2700. He was so happy. He said since I did this than he would give me money that I need to go to LA in the summer.Well now the time comes and he cant? i just found out he offered to buy my stepmom a car w/ the money i raised for the house to get fixed.& my mom got me a car so i can get to school & back and he was supposed to fix w.e was wrong w. it since he didnt buy it. Wel he cant do that now either. But he can just buy my stepsis a car for her b.day Ydoes he do this to me?wat do i do? I want him to feel like he deserves