Would you say am depressed?

I feed sad every now and then. Sometimes i wish i didn't exist and i over-think situations and sometimes become sad... When in the public i tend to 'be' happy and joyful, but alone am quiet and so tried. I have trouble sleeping. I sleep late and wake up early and i try not to sleep again until 10pm but end up awake on my bed thinking about situations and other stuff. I usually stay awake till past 12am. i cry at things 'normal' people wouldn't and i don't cry when others do. (e.g someone pushed me onto a brick wall and i got a deep scar on my hand and a fat bruise on my knees - i just got teary and smiled) i dont know am usually so energetic when it comes to goin outside but when with my family or home am the opposite. i dont plan to kill myself or anything i appreciate life but i just question why i existed the first place.