My friends always exclude me?

So my friends always invite me to places Individually and they invite me to parties but when it comes to things like group sleepovers and handouts they always include all of my friends but me and it's rly annoying. When I'm doing something with my friends That's really fun I try to include all of my friend group but my friends never want to include me. They always make plans without thinking of asking me . And then if I don't invite my best friends she gets pissed when she's the one always making plans without me and today my friends were having a sleepover after a party and they didn't include me so I felt rly left out coz I spent my Friday night alone and I was kidding about how I was a little jealous and I made up an excuse saying I wouldn't of been able to go anyways and now my friends think I'm all bitchy. When my best friend is the one who is like forcing me to take her to six flags coz shes jealous im gojng with my orher friend but when i told her i dont want to take her she thinks im being rude and just tryjng to get back at her when reality is i just want it to be me and my other friend UGHJ WHAT DO I DO?!?!