I always feel unlegitimate because I don’t always feel depressed. When I feel bad, it’s for real. I start having really dark thoughts, I cry a lot, I just give up on everything, but then I have some highs, so the point where I feel like I’m going to explode. It feels like the inside of my body is shaking heavily, a weird mix of overexcitement and anxiety. From what I’ve read, that’s not a symptom of depression. 
I just want to add that I am not bipolar. I thought it may be an explanation but my moods swings happen way too fast( like, a few hours).