Replying to I don't know what to do about this girl (18 yrs old)

Hey NS I turn to you in my time of need as you tend to be the most knowledgeable regarding these types of things. I will try to condense this story as much as possible but you must understand it is long, detailed, and has consumed the majority of my high school experience. All of the people I mention actually don't go to my high school but go to one nearby EPHS. AT the end of sophomore year I met this girl named Emma , she was friendly, funny, and had a great body. We were both interested in each other and whenever we would be at parties we would gravitate towards each other, however being the person that I am I was too nervous to ever ask her out or even put my arm around her. The summer after sophomore year she began to loose interest and next thing I knew about a month into junior year she was dating one of my closest friends named Blake. We didn't talk much but in January, I had to go over to her house for some reason (i forget) and for 8 hours we just talked, she confessed she had feelings for me over the entire summer and was heartbroken that I never made a move. That day ended on an awkward note but we did begin to talk more like good friends. But I was now in a situation where I had feelings for my good friend's girlfriend. Because we talked more constantly I had to hear her tell me about giving him head and sending him pics, which was very hard for me. They broke up in march of junior year and between then and now (September of senior year) shes's fallen for 4 different guys, hooked up with them, sent them pics, (the works). But throughout the summer she's kept texting me about this new guy, how great their relationship is, all the fucked up stuff they've done, and then it ends with me helping her through her breakup. I met this really nice girl who was perfect for me in July but I had to end it cause I was just so hung up on Emma. So there I've tried to move on but I can't. As of right now she's trying to mend together a relationship with another one of my good friends (Adam) because " he's the only guy that treats her right" when I've fucking been there for her through thick and thin for the past two fucking years, and this guy has literally cheated don her and told her he's no longer interested. I'm burnt out and feel like I just need to come clean to her but it's just such a bold move. I feel like I'm in the friendzone now but I don't know, If any of you older guys have been through something similar I would appreciate input.