Yeah I know how you feel. That same thing kind of happened to me. I got back to school and I was like wow. F this, first period I was like ... now I re-realize why I hate this place so much. It brought me way down and all I wanted to do was sleep. Everyone else was so energetic and I just didnt want to exist that day.
Keep your head up, and just dont give up. Nothing lasts forever. :]