Some Gay High School BS

This might be a long one, but I really need some help from you guys. OK, so I'm a freshman in high school, and I am gay. Me and my ex-best friend (let's call her Sarah) started off the year really great. We were really close, but then I developed a crush on one of the sophomores. (Let's call him, Keith. And he's straight BTW.)We've known him since we were in 6th grade since we all went to the same middle school, and I was starting to get really attracted to him. Of course, with Sarah being my best friend, I told her who I was crushing on. She told me her crush, and it all seemed normal.I texted him on snapchat if he wanted to be friends, and he said yeah. I told Sarah this, and afterwards she texting him too. Asking to be friends. At this point, she was hitting it off better than me because I'm really awkward around guys. I get kinda triggered, but I get over it the next day.We're in our lunch period and I see that Sarah was texting my other friend. (Let's call her Erika) I am suspicious because everytime I ask what they are talking about they turn off their phones. I'm not stupid so I come to the conclusion that they were talking about me. I leave and a few minutes later I come back, to snoop through Erika's conversation to see if I was the topic of the conversation.Yep. I was correct. Sarah apparently had a crush on Keith, but lied to me to get me to spill it first. She knew that I was triggered last night because she was becoming better friends with him. So you know what she said? She said, "Keith is straight, Alex has no chance." and "I feel bad... but then again I don't."I caught them both in their act, and I confronted them. (Not like fighting them, but I talked to them about it.) I was really mad at this point because Sarah was my best friend and I see that she is lying to me, talking about me behind my back, and liking the same guy I like. (On a different note she always says that she wishes she could change a few things about him, while I think he's perfectly fine. So who sounds less bitchy?)I dropped Sarah, and I started texting Keith so Sarah couldn't get him first. Me and Keith start to hit it off, and we become really close friends. (In 2 days, like wow I have trouble making friends in a year lmao.) My feelings for him start to die down, because I know see him as a friend I can depend on, rather than a lover.So this was like Monday, and the day I'm typing this is Friday. Today at school I was walking to Lunch with my friend Liz, and Sarah tagged along because she's friends with Liz. Keith says hi to me, and I say hi back. (Ya know, normal greetings and stuff.)I didn't think anything of it until I remembered that Sarah liked him too. Since I knew she was fake, I thought that she would've been really jealous. A few hours ago, me and him start texting and around a half-hour ago, she texts him... asking to be friends.I told Keith about the thing that happened with Sarah and Erika, but lied about who the crush was, because I didn't want to tell my straight friend that I had the hots for him. He accepted her real life friend request because he didn't want to be rude, but now I'm scared that he'll get directly caught up in the drama.He doesn't know that I liked him, and if anything goes badly, Sarah will most likely expose me to him. I told him to be friendly, but don't get close with her, just to keep things safe. But, I really don't want to lose my closest friend at the moment, due to a petty girl releasing a feeling I only had for about 2 days.What do I do? (Sorry this was long as heck.)