Chances are unless you are very lucky you will go thru many different relationships before you find your special someone. Finding your sole mate is like gambling... In poker and blackjack you may have to play dozens of hands until you get a winning hand, and it is the same with relationships.
During your life you will probably meet some people who seem like they may be the one, or that they are close, but still have the feeling that something else is missing. My advice is that if you are not happy, because something seems like it is missing, then it usually is not right.
Before I found my special someone, I was in a relationship for over 10 years, and I thought everything was great, until I started to seriously consider getting married. Then I noticed that we had so little in common and in reality wanted so many different things out of life and one day we both realized there was much about each of us that we both wanted from someone, but it was not us that we wanted.