my family rejects me, my mother hates me, my father's too
im alone in USA, my parents rejected me cause i was supporting my bisexual sister, my parents are very homophobic and hates my sister too

Don't give up. Family is not necessarily is who's releated by blood, but by trust, respect and love - you can get way better friends than an abusive parent ever can be. It's a really admirable thing you did towards your sister, don't let others belittle you, or her about it. Try to find stability in her, or friends you can rely on even just on the level of talking to them and being there for you. You mentioned how many girlfriends you had - I don't know your age or how serious your partnerships were, but frankly it sounds quite a many, it hints that you want to have someone - to not to be alone, or to have someone for you? It's really understandable, but as the saying goes (or not, I'm bad at quites) be the person your love wants to be with. If you don't have stability in your life, girls who are not attracted to a stable relationship will end you with, and sooner or later leave, sadly. Don't forget that girlfriends who cheat on your or parents you reject you give away about their personality, not about yours - it's a really hard concept to grasp if you're feeling down, but their oppinion and behaviour does not mean that they are right in that way.
Stay strong, and if you feel like it, reply here, or if you prefer that on my giveaways somewhere, or add me on Steam.