I don't know

Hi
I don't know why I'm posting here or what I'll achieve by doing this but I just need to let this out. Writing in journals doesn't help and talking to my best friend doesn't seem to be an option to me.
I've been feeling sad for quite some time now but I can't find a reason why. My life is completely normal. I have nice, loving parents, some very good friends with whom I can share literally anything and I know for a fact they'll try to help me. But that's the problem. I don't know what to tell them. I am sad but if someone asks me I don't know what to tell them. I have completely lost any motivation I had in my previous years and I used to be quite motivated. I have lost every hobby I used to have. My attention span has gone to sh**. My memory has gone to sh**. This is happening at a very crucial time in my education.
I even have a very important assignment due tomorrow but I just can't find the will to do it. Where fear of failure used to drive me earlier and I would have completed my assignment easily, now I can't even get me started. I've completely lost that fear and for lack of better words just don't care anymore. Where before I used to top my class, now I'm just average. And the worst thing about this is I don't care. I don't understand why I don't care.
I've tried everything. Watched inspirational videos, read solutions for procrastinating but nothing works. After a bit I go back to the same blankness. It's not like I'm doing something recreational. So basically this has had a very negative impact on my education and probably my career in future, and that in turn further "saddens" me?
I can't or probably don't want to go to my parents or friends with this because let's be honest- what even am I going to say?? That I'm sad? They'll ask why and I don't have an answer. I seriously don't.
I don't have any particularly suicidal thoughts but I do have a feeling that I want to stop existing. I don't want to kill myself, I don't have the guts but like just randomly stop existing. Plus I took online tests for depression and I don't have it, I'm sure of it. There is no major bad incident that has happened in my life and like I said if I go talk to my parents or friends, they WILL try to help. But that' s what scares me. I really feel I'm being very dramatic here and trust me, I really really don't want to feel this way. I have no issues with attention. I don't even like attention. And all my friends will tell you I avoid drama at all costs. I know these things about myself.
And yet I can't figure this out. I don't WANT to cause any unnecessary situations and I've been trying to wait it out hoping this will go away. AS for now- it hasn't.


If you've read this, thank you. You don't have to reply. I just needed to do this.