Why are my friends mad at me?

[Jacki]

So, this weekend my whole group of friends went out to see a movie and had a large sleepover and didn't invite me. It hurt me because they are my closest friends. It seems that my best friends try to make me jealous at times and it is so annoying. They didn't even invite me and they keep posting pictures on social media. Now, it seems that they are mad at me but I didn't do anything. I'm the one who should be mad at them in reality. Ugh my friends just piss me off sometimes. I have a feeling they talked a lot behind my back at the sleepover, and that hurts me because I would never do that to them. Does anyone know why they would all be ignoring me and acting like they were mad at me? I'm going to school tomorrow and I don't want them to ignore me during school. Can someone explain please???! (I'm 14 btw)