relationships

I'm turning 20 in a couple of weeks and I have yet to be in a relationship. I mean I can understand why I didn't have one in high school, but now that I'm in college it doesn't make sense. Granted I may not be the most approachable person due to the fact that I'm quiet and shy when people first meet me, but once they get to know me I'm pretty outgoing. Despite me flirting with a guy and us talking more, I always end up in the friend zone. Not being in a relationship, let alone experiencing it, has taken a toll on my emotions and how I perceive myself. I just really could use some advice and maybe there's something that I'm doing wrong in this whole situation. I just really could use some answers.