@SilentlyFading,
I remember 18 as being awkward, too (I'm 50). So understand that some of that is kinda normal.
A few ways to get more confidence -
* do things you're good at. Whatever they are. Can you bake? Paint? Square dance? Jump rope? I dunno. But positive experiences help.
* consider a class in either acting or public speaking. These can help with shyness and confidence issues. You will likely never be on Broadway or address an audience of 100,000, but you may find it's easier to talk to people.
* take the initiative in relationships and friendships. Waiting around for a guy to notice or be interested is so nineteenth century. If you approach people, you will know what they are thinking, yes? And BTW, there may be guys who you think are awesome who are a bit shy around
you.
Go and be awesome.