Help, with the girl I like and a few life problems?

[Mister Mike 21]

First of all, the girl I like recently went to a sort of club, and kissed someone she'd never met before. I felt gutted for hours. We used to be really close but now we don't talk as much. I feel like we've grown apart and I really want to change that. Things like twitter have meant she's found new friends and talks to me less. I try to start conversation with her often, but she never tries with me. I see her telling other male friends to check their phones etc. Also, with the girl I like there is a group of friends that I find really cool and I consider myself 'in their circle'. However, over a few days in the summer I haven't been invited to the things that they went to, and it makes me sad as if they don't like me and they I don't have any friends. Also, I feel like I'm boring on twitter, as if I have nothing to talk about on it, this also might be why we've grown apart. What do I tweet about? Lastly, I keep thinking that I'm boring and my conversations are rubbish.

PLEASE help me. I have seriously considered ending it all, but I know I wouldn't.