Is this a sign of depression?

I'm a college freshmen and recently I've been suffering from what seem like signs of depression. Starting in the last month or so I've lost all hope for everything. It started off with me telling myself that I wouldn't get involved with guys because of my intense fear of rejection, and I was very bitter and cynical towards all of my guy friends when I didn't want to be or didn't mean it. I was fine though even then. Just recently, in the past few weeks, I have suddenly become emotionally and physically exhausted. I feel like I never get enough sleep. I end up taking three or four hour naps during the day and then wake up at around seven and sleep on and off all through the night. I'm too sluggish and lazy to get to cl in the morning and I have no drive to do anything anymore. I don't workout anymore. Even just thinking about it makes me cringe. I'm moody and irritable and have noticed signs of self-loathing. I'm not content with my body image anymore and often have thoughts of doing dangerous things like eating incorrectly (which has been a flaw of mine in the past that I just recently got past). I can hardly concentrate in cl and am failing two simple cles. When I'm not drinking alcohol at parties on the weekends I'm always wishing I was, because thats the only time I don't feel so bad. The weird thing is, I can got like this for days and days, all upset and tired, then some days I can be happy again like nothing happened. Recently, though, my bad mood is not going away and all I can do is sleep. What is going on?? Any help is appreciated...thanks.