I was where you were, so I know what you mean. I only figured out what I really want from life in the last year or so, and I'm 28.
A really important thing to ask yourself (a lot of people fail to do this) is whether or not you are pursuing something in your university studies that you really enjoy. Are you slaving away at school just to get a piece of paper, or are you really working towards a career that you really want and know you'll enjoy? If you're not, all that time at school feels like (and maybe even is) a waste.
Secondly, write down the things that you feel are things you absolutely MUST accomplish in your life. This could be travel, learn a language, learn to play guitar, whatever. Figure out how you could work these things into your life without causing too much interruption to your work/school schedule. It will add some enjoyment and sense of accomplishment to your life.
I spent four years slaving away in school, not knowing what I wanted to do. So I dropped out for four years. I did a few of the things I felt necessary to make me feel like I'd accomplished something.....one of those big things was travel. I felt better about myself, and in the process discovered the direction I wanted to go with my future career. So now I'm back in school, working towards that.....there's a goal in sight and a sense of purpose. As I go, I'm slowly adding in little things that I deem important for my happiness....for me right now, that is learning how to golf.
So just think about it. What makes you happy? Pursue happiness, and you will always have a sense of purpose.