Is it normal that my default state of emotion is slightly depressed?

Here I am, its 4 am and Im staring at a monitor again. Im exhausted, but I can't sleep. I have lots of happy moments, but they're all so fleeting, and as soon as they're over, I find myself saying, I shouldn't be feeling this way, but here I am, feeling a little depressed again. Why is this my default emotional state? I am good looking, smart, talented and endowed in ways that would make most guys green with envy. I have used lots of friends, now, not so much, but I have no true friends, save for the girl I love. I feel empty, hollow and soulless inside. Ever see the show Dexter? You know how he monologues all the time about having to wear the mask all time when he really feels nothing at all, or just feels confused, or disgusted toward humanity? I feel just like that. I usually stay up so late watching that show, because I feel like finally, theres someone to relate to. Or another relation, Greg House and his hatred for humanity and the endless useless social niceties that are forced down are throats, that if we dont fully indulge, people think youre an ass, or that you hate them... idiots. I imagine ways to kill people and all the possibilities of hiding the body without getting caught, it'd be so easy, and it confuses me that I feel nothing at all save for relief and decompression in these fantasies. Of course, I could never truly kill someone. I feel so empty. I just can't get over the fact that everyday, my default emotional state is depression. Also, I no longer see any meaning in life, which is confusing. I've found love, found purpose to forward the field of biotechnology and become successful as an entrepreneur in the field. The Singularity is near, but still, life seems so pointless, where's the meaning? I dont think I have an addictive personality, but I am nonetheless prone to addiction because of my emotional state. Particularly to things that cure it, which include the girl I love, whom, whenever I am around, makes me feel happy continuously. Another cure is marijuana, which I love, but don't want to be come emotionally dependent on. And finally, whatever makes my ego trip, girls who make me feel hot, who crave to get in my pants and actually do it, hookups, dancing with them, whatever I do that makes them get off or go "dayummm" and fills their stomach with butterflies. I don't know. I'm depressed and horribly lonely, the girl I love is going to college an hour away from where I am, which I am slowly coming to terms with, even though it hurts. Shes really the only healthy thing that takes my pain away and makes me a happy man. Whenever I'm with her, its like my heart is floating in the clouds for the day, and I dont come down and crash till about an hour after she leaves. Anyway, is it normal that my default emotional state is somewhat depressed?