numbness..confusion

Ive never had it down on some medical paper i suffer depression but my therapist did talk about it before and so on, last year was a rough year and the year before i was self harming failing school and just generally all over the place, this year i thought would be different but im so empty inside, ive lost alot of my humour because half of the time im in a daydream, i still get hyper and laugh my head off but then i get very down and literally empty like im not in control and i hate it because if i dont feel anything how can i change anything? So im in an important year in school and I need to focus but I cant because dark thoughts consume me and i havent told anyone at all, not one person knows because i cant describe how i feel, im not like this because i got abused or bullied, i just feel this way with no definite reason so i dont want to say it, i really want to talk to someone but every chance i get i blow, i either say im tired or im good or im just being moody and the cycle continues, its only the beginning of the school year and ive wanted to harm myself again (thats another topic), ive had really good days and really bad, like getting out of bed is so hard sometimes and talking is hard just living, i dont know whats wrong its killing me