Why has my fear of the dark reappeared?

I know I recently posted a similar question but I'd like to give a little more detail and ask for more help. So I'm 13 years old, I live in a house with my mom and brother, and I'm terrified of the dark. Whenever I turn off the lights I always think I see something in the dark, like sometimes I see a box as a little gremlin or something. But anyway this used to be a problem when I was smaller, but I got over it at about 8 years old. But since my moms divorce I can't seem to stay in the dark for more than a few seconds. I know there is nothing there, but my mind always forces me to turn the light back on. Any help please?