I have no friends and no one talks to me anymore?

Maybe you should try reaching out to the people you know and make the first move. If they continue to act the same then you've done what you can and you should consider though, who you want to be friends with and also maybe evaluate yourself and think of reasons as to why people aren't as close to you than others. Understand that maybe you've done nothing wrong and you're just in with the wrong crowd. Another option too is I've found many friends online (as long as you're careful of course) that have become very close to me. I'm 18 too and if you want we could try talking and being friends, I check my answered questions often so just reply if you want. 

I'm sorry you are going through this and I hope something I say will help! 

To have a friend, you have to be a friend.. obviously, I don't know you, or what you may have done to be a good friend, but you don't mention in your post that you have ever called anyone, or invited them over etc.. you only mention that you are waiting for others to befriend you.. this may not be the case, it could be that you just didn't mention the effort you make, personally - and we are just not given enough details to make any suggestions. 

So, all I can really say is this: if you are kind, thoughtful, reliable, helpful; if you remember to call those who are having a birthday, or have been sick, or text someone else who you think might be lonely, then your chances of having a friend go up dramatically! People want to be around someone who listens, who shows that they care. 

I am wondering if you might have done something a bit alarming, that people are lowering their voices, nervous about telling you things? If that is the case and you know of something that you might have done, then you need to talk about it with those you hope to have as friends.. 

But there is another possibility here too - I tend to be an outgoing person. I just changed to a new church, and have tried often to call others, to say hi, to invite them over.. but as you say, they have their own set of friends - yes, it makes me sort of sad and feel left out, but all I can do is continue to reach out, and do my best to be a good friend. It has been my experience that you only really need ONE close friend, and life can be just wonderful! Think of someone you want to have as a friend, and concentrate on that one relationship. Think of joining a group, or a church! These can be great place to meet people.. bottom line, you just need to be doing your best to be a good friend to others, and hope for the best. :-)