What is it like when I'm obsessed about something? Does my thinking follow a pattern?

Yes. Obsession is a cycle of thoughts that continues on it's own even though I don't want to have the thoughts. When the obsession cycle first starts I can recognize that the thoughts are not healthy or rational. It like a separate part of my mind that has it's own will. As the obsession continues it becomes all encompassing. It fills my mind more and more even as the thoughts become less rational. I can not think other thoughts or do other things until the obsession is relieved. This leads to an endless cycle where I can not accomplish much of anything because the obsession demands constant attention from me.