I JUST REALLY NEED SUM GOOD ADVICE RIGHT NOW. PLEASE HELP?

Well just to start off Im 18 years old. go to beauty school & I live at home with my mother and 2 brothers but its just so hard. my one brother who is 24 and an alcoholic, i just cant seem to get along with. He's always putting me down and even though I pretend to be thick skinned I am actually very fragile and tend to let peoples words really get to me. While in private he says things like your worthless, your getting no where, etc. but then will try and make it seem like he is the victim in front of others by trying to give hugs and the truth be told is that I dont want to hug or pretend to love someone who continually puts me down like that! my feelings are to damn hurt to pretend! then just about 2minutes ago he came into the living room where me my mom and brother are and kisses them and says How much he loves his family then looks at me and says "but not you, you dont belong" and words like that really get me down cause I recently found out I was adopted Oh Yeah but let me continue, so then he kums over to hit me on the head I suppose but I quickly blocked it and pushed him back (hes only like 5'7) and my mom was like "oh my goodness why did you do that to him? why are you so nasty?" and I jus kept quiet kuz I knew if I spoke up Id begin to cry kuz I just cant handle this pain anymore. what can I do? I have no job so I kant leave