I really need help...

My own family and friends are against me and I really dont know what to do anymore...Im thinking of so many things. The family member I trusted the most, my Sister, decided to choose her "friend" over me. She promised she chose and believes in family first and yet ends up choosing her stupid friend who did nothing but steal everyone including my sis from me. My sis and I were really close since we were kids..we even hanged out together at school with a group of people who I believed were my friends. But they ultimately turned out to be fakers who didn't care if I'm with them or if something happens to me. The other day for example, we decided to ditch to this place together but they ended up leaving me and I almost got in severe trouble because I was caught. Once I got on Facebook I saw that they were all messaging as if nothing happened and I ultimately decided to keep my distance and I left it. Now heres the part that really hurt me...My sister I guess pretended to help me talk to them again and ended up showing me some messages from that "friend" of hers where she stated that she was once jealous of me because I was social and had some friends while she did not. I expected her to defend me but all she could message was that I had problems and that I was just like that. The others in the chat agreed that I was the "jealous" type and they dismissed the topic easily. She also told me all these things about how they were looking for me the day we ditched and about how they really were "worried" at the time. I kinda believed in her, and I was kinda happy again to be honest. Then all of that went down after. She re added me in the chat and no one seemed to notice that I was back and so out of frustration I left. Before leaving I sent a message about why I left the chat (the incident with the ditching) in the first place and all that happened was my sister's friend leaving the chat too. I know I shouldn't of done this and I truly regret it but I checked her messages and to my surprise my sis had quickly rushed to cheer her up despite her tellling me that she hadn't messaged her at all. I even found out that rather than protect me she agreed with her "friend" that I was a nuisance. This really hurt me and upon finding out I rushed up to my sis and told her everything. I called her a liar and a traitor and she wouldn't say anything. I know Im wrong for checking her messages but apparently that was all she cared about. I told my mom about this and all she did was tell me to solve my own problems and do whatever I wanted and she ended up taking my Sister's side again. I told her I was probably going to switch schools because I really cannnot bear feeling like this anymore and she said she didn't care how I felt and that no matter what I had to protect my sis. My dad then got up and looked as if he was about to beat me and asked me what was going on. My mom intervened and thankfully nothing happened...However she told me that from now on my sis and I are split from hanging out ever again at school. My sister agreed with her right away and I was devastated...My mom and dad always believe her...and I trusted my sis and she ended up betraying me. My "friends" did too. And im pondering whether or notto run away from home. It hurts because I feel alone and the only person I trusted betrayed me and I feel that right now she along with my "friends" are in that chat acting as if nothing has happened.. Im really about to explode out of anger and sadness and I feel like I can do anything to stop this pain I just dont know how to deal with any of this anymore. Multiple responses would be appreciated. What should I do?