Ever since I can remember, I’ve always had an idea for a job or goal I want to pursue. As young as 4 or 5 I was choosing a career, becoming obsessed with it, then dropping it weeks later. This behavior could be normal for a kid, and I know that, but it’s still happening. I’m 16 and I, to this day, become completely and totally obsessed with something, whether it be a job, person (usually serial killer or author), or religion. I get completely obsessed with a job and research it for weeks, then decide I’m not ever getting a job or I’ll work for a non-profit fox refuge. For months I’ll go on believing strongly that there is no god, being completely and totally atheist. Just today, my entire belief changed and I’m now looking at a new religion (even though the one I’m pursuing doesn’t necessarily require a god.) Another thing that completely changes is my mindset. It can change in weeks or days, but the change is always extremely dramatic. One second I’m dead set on going to college, medical school, become a criminal psychologist. The next day I can be completely changed, thinking things like “School doesn’t matter I’m the grand scheme of things” “I should just leave, run away. I should live in the fields and make a living off selling jewelry.” Crazy stuff like that. These mindsets are so dramatic that it’s becoming strangely exhausting to keep up with myself. 
Is this a mental illness of some sort, or is this normal? 
I have depression that is for the most part treated and have mood swings that seem to be incurable. I also have a problem with self harm and have a history of anorexia. (Just some background)
Thanks for reading! :)