You're most likely not depressed. Most don't know what depression is like and will hopefully never experience it. I, myself, have never been affected by it, I thought I have, but I haven't. I do, however, know many people who have faced and, or are facing it now. Really all they did/are trying to do is stay positive. Do not think the world is coming to an end because you're sad lately. There is always a light at the end of the tunnel, unless you do something to cave yourself in, don't cave yourself in. Find things to occupy your time, productively. Things that benefit you, and you'll feel good for doing afterwards. Also, never think people don't care about you. People can be mean, but that should never bring you down. People are sick, unthoughtful, and careless towards others sometimes. Its sad but true.

Just keep your head and goals high, and determination strong. You will stop being sad, you'll find things that will make you happy. Its not something that happens overnight, and with no effort. You have to be patient and determined. You are the only one who can pull yourself out of a sad state.