Mood Swing

I'm 19 in college and for the past few months I been experience a huge mood swing. One hour I would feel like the most depression person I would cry out of no where and feel like the world is ending, I can't think of anything but bad experiences and one hour later I would feel like the happiest person and everything going great and it would go back and fort in one day. I didn't really notice it before, I though I was just being upset then happy but until someone brought it up to me. So now that I think about it I cannot control it at all. It made me scared then confidence upset to happy, happy to mad. How do I solve this problem? And why did this happen to me?