Firstly: I am not officially diagnosed as depressive.
I am starting to see a therapist, after months of being told that there is no point, all I need to do is think positively. I am a man, 19, and in studies (that I am failing).
I have talked to my mom about how I feel. I am close to her. She has said to me that she understands, and that all she had to do was "flip a switch" to see the world differently and feel better. My dad also. She says to just try and appreciate stuff, like for example when something tastes nice, or something beautiful. But I find myself trying to, and not being able to do so consistently, and sometimes I just can't. Most the time I just don't care. Ok that's great, but what else? I feel like I am extremely ungrateful for my life, and that more broadly, I Am wasting it away. I never was a particularly positive person, and I was always prone to being miserable, something my parents never understood why, for what reason. A few months ago I went through a messy breakup, and since then I have felt overall miserable, but this nearly all the time, not occasionally. My self esteem has plummeted, people have noticed my "dettached" mood and quietness.
I don't speak up when I want to anymore, I think twice about every action I make, and doubt myself so much to the point of not even trying to do something (studying for an exam, etc) even though I know that if I tried, I could, because I've done it before most of the time.
It's affecting my life, I won't be able to continue studies with my bad results, which leads me to think I'm a failure, which leads to feeling of extreme guilt because I don't even try.

I just don't know what to do. I'm lost. I don't know what I expect to gain from posting this here.
Sorry for being long