What is this emptiness I feel in my life?

I'm 18 and going off to college and all.. I'm a good student and I have some very dear friends and a supportive family... but I just feel so lost. I feel empty inside and kinda worthless. I've had some thoughts of suicide but I really don't think I'd dare to do it. I haven't gone through any break ups or deaths of loved ones, so I don't really know the root of my problem. I have alright self esteem it's a little low but it's gotten so much better through the years. But I feel like I am missing something in my life and it is driving me on the brink of insanity...