Winter
I've noticed, a extremely common issue probably 90% of the population has with it without knowing. As a writer you set high standards which are harder to do reach at any level. Every book is gonna have flaws, whether it's with the plot progression base or the fluidity (smoothness) of the story. While as this will always be an issue and some people would say they are the best writers denying advice from readers who can be new or old. But when your writer you books you have the tendency to second guess which causes you self esteem to lower, but one thing that make you differ is your actually trying to get better whether it's advice or just asking how to improve to make your book for adoptable to your readers. With this being said, keep up the great work and trust me within time I wouldn't be surprised if you could hit it big if you continued. Or even if you want to do this on the side, you show a lot of resilience alone with handling both school and writing with a mostly consistent schedule. Your doing amazing and good luck for anything you plan to do in the future.