Is It Depression Or Just Melancholy?

So right now I currently don't know how to deal with my emotions. I don't know if it's depression, or if I'm just stuck in a melancholic trance.  Right now though I can't stop thinking of a certain girl, you all know who it is. I know she doesn't think of me though. But when I think of her I become melancholy. When I'm not thinking of her I'm sad. I'm sad just because well she's not my girlfriend, no matter what happens she'll never be my girlfriend or anything more than a friend for me. Thinking of her just makes me sigh and moan. All I can ever do is moan about her to my friends when I have nothing else better to do. And right now isn't a good time to be in this condition with my dad's return to the hospital. Despite his being a useless sack of shit I still care for him on some level. But this girl, she's going to be in my head forever on. I won't forget her, it's impossible. I'm just well in love. Pure and simple, I'm in love. Something as simple as contact with her brightens up my day. I'm in a better mental position than I was when I started this blog also. When this blog was started I was so deeply depressed over her hating me for my friend's antics. Now I'm in a better state that's deteriorating except this time it's out of loneliness. It's starting to kill me. I have many friends, yes I do. But, I don't have a girlfriend that I love and cherish. Don't think I will find one either, except in her. Oh well, I still prefer to live life day to day.