Not able to concentrate on anything.

I started it just for fun but, then I quickly became addicted.  More I take drugs, my addiction level increases.  I was not in control. The drugs controlled me. When I saw it in front of me, face to face, I couldn't stop myself. Now-a-days I sleep all day in the classroom.  If I go around thinking that I will stop it, I can't be able to do it.  I am rally looking for a way out.