Why am I depressed for no reason?

Im just saying whats been happening to help you guys help me with the problem

I just recently broke up with my boyfriend(now ex) 2 weeks ago. I have NO feeling or love for him, and im not saying that to make myself feel better im 100% sure im over him. A week after I broke up with him I decided I dont want to be in a relationship for years.

As bad as I want a guy, I stick to just crushing on guys and acting like one of those teenage girls fangirling over guys in their rooms with other girls. I got a new kindle fire and I downloaded 2 books. The first book is "Silence" and the other is "Broken Silence" (broken silence is the sequel) the book is a heart breaking story about a couple who has known eachother since childhood. I finished the first book (Silence) and it had an ending that caused me to cry.

Now im halfway through the sequel, which is basically continuing from the tragic moment from the first book. At the part where I am, its when the girl moves to another country, far away from the guy(im trying not to spoil the book if you plan on reading it). The book is very funny but a lot more heartbreaking and has a lot of detail in it. I stopped in the middle of the book and I plan on reading more next week because I cried soo much when I stopped reading.

whenever I read the book I think about how I wanted my ex to be the same and for some reason, I just wished I was the main female character in the book. I kinda wanted to feel the same love and affection as them. I know I sound kinda selfish, but I tried to get my mind of the stupid book as it had way to much detail, so i got a perfect image of what was going on in the book.

Again, I know I sound selfish, but now im on the computer staying AWAY from the book searching up random crap to get my mind off the love story. As every second passes by I become more depressed for no reason, and I cant seem to figure out why im depressed. I tried calling my guy friend who is great at making me laugh. we talked for hours and i did laugh a lot, but after I hung up I was depressed again right away. I even feel like the story is shoving the fact that im jealous of the fake characters and I'll never feel the same love as them in my face

Please no rude comments, those will just make me more depressed. (extra information:im very sensitive and get mad or upset easily) any explanation for my depression telling from what you've read?