Depression? What is it?

So.
I had a blast this weekend. An absolute blast.
Went to Chinatown. Watched some movies. Chilled. Cuddled. Danced. Rode the C-Train.
Played with Balloons. Yet, despite the grand time that I had. I had an underlying feeling of just utter saddness. Just no matter what, i was not happy happy. I was not my usual self. Everyone asked if everything was alright. The answer is no. I just want to sit here and cry. I don't want to move from my room. I just want to curl up with my depressed music playing and just sleep or read. I don't want to do anything else. I don't want to eat. *Sigh*
Anyways, i am going to go and be all emo and depressed now. Ciao all.