Am I being bullied? Im not sure?

I don't wanna make a fuss, but I don't want to b put down anymore. I'm wondering whether I am acutally being bullied or I am jsut being stupid. They constantly nit-pick, fault-find and criticise me, they attempt to undermine me and I often feel worthless. They also isolate me from the group and we are suppose to be really good friends. One had a party and invited all of our group apart from me. They always seem to find something to have a go at me for and always humaliate me in fornt of everyone. I don't know what to do, everything i say to them they seem to take this mick out of and never take anything I say seriously. If this is bullying and I go to someone they will not take it seriously and take the mick out of me even more. I dunno.