With so many people saying "You're 18, you don't know what you want.." and what not, and I thought I would chime in. I met my wife in high school when I was 17, and we dated 5 years and have been married just under a year. It's easy to write off a teenage relationship, but if you really have chemistry with this person don't sell yourself short simply because the both of you are young.
How old are you though? I agree with part of what you're saying, because some people are mature or smart enough to see these signs, while some aren't. There are generational differences though. The hardest thing I ever did was move on from someone i thought was "the one"...but I am very glad I did. It's true though I think for the current generation, a lot (not all) don't really know what they want. People seem to be just a little more "disconnected" from one another, or that's my perception.