Need friend advice HELP

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I dont know if its just me being too sensitive or what but lately Ive been feeling so down about my friends, like they arent friends at all. To fill you in, I have 4 absolute best friends, no single bestfriend or favourite or whatever, lets call them Milly,Molly,Holly and Polly. It started when i found out from another person that Milly slept with the guy I was sleeping with and fell for hard and ended up getting heartbroken, and was just recovering, she lied continuously about it until i finally broke her and she said it. I was really hurt and I expressed this too her and then I found out she told this guy everything I was saying, I was more than embarrassed! Meanwhile Molly, Polly and Holly knew about this and didnt tell me until they knew I found out. Molly was even at Millys house when it happened! And then I tried to heal everything because thats just who I am, but then I found out Molly was doing the same thing to Polly! Still trying to fix things, I try and do stuff with them but they always leave me out even if I ask to come, like concerts which Milly and Molly said no too me coming, then they let Polly come, and Molly was going on holidays to the beach and I asked if I could come and she said it was too full because her brothers friend is going and today i find out Millys going with her now!! Seriously just makes me so upset I have no one other than family, which I cant even talk too. Is it just me or are they crappy friends?