Feelings of no emotion?

I am a 14 year old male who does not lead the life of a typical 14 year old teen. I go to one of top high schools in the United States, one known for its notorious workload. This does contribute to a lot of stress, but I've been able to handle relatively easily. This summer, I've had depression. Not diagnosed, but I've felt sad for about four months straight, with only a few days of happiness. For the past three weeks, my depression has been non existent since I've been eating foods rich and omega and just staying healthy. One day, I slept at 3:45 at night doing homework, and I could not sleep. My mind was NOT calm when I was sleeping, it was very active due to the amount of homework I was doing. When I slept, my heart raced a bit (I don't know why) and I couldn't fall asleep. Everytime it seemed like I'd drfit off, i felt like i was going to die and never wake up. Perhaps I was just too tired and was over thinking. Well anyways, I did not respond fearful to that event or i didn't become depressed, which was a very good sign. But recently, I've felt that all the emotion from me is drained. I still laugh while watching comedy shows a bit, but I'm not genuinely happy or sad, just zero emotion whatsoever. I'm super worried that this will last forever, I don't want to have this happen! Is this a part of depression showing that I haven't fully healed, and will this ever pass? What can I do to improve my mood. And it's only been a few days with my lack of emotion and I've been a bit sleepy recently (only getting 6 hours of sleep a night) Am I over thinking this? Am I just really tired? PLEASE HELP! i'm so worried :/